Firearms Glossary

Plain-language definitions of the terminology you will encounter in our classes, at the range, and online. New terms are added as our content grows.

By Category

A to Z

A

Absolute co-witnessOptics and Sights: At absolute co-witness the iron sights and the red dot superimpose exactly. This yields a clean backup sight picture if the dot dies, at the cost of the irons cluttering the lower half of the optic window.; See also: Co-witness, Lower 1/3 co-witness
ActionFirearm Parts: The action is the working heart of the firearm: the set of parts that chamber a round, fire it, and extract and eject the spent case. Action type (bolt, lever, pump, semi-automatic, etc.) determines how the gun cycles and how fast it can be fired.; See also: Bolt-action, Semi-automatic, Striker-fired
AK platform (AK-47 / AK-74)Action Types: The AK platform is a long-stroke gas-piston rifle system developed by Mikhail Kalashnikov in 1947. It is famous for reliability under harsh conditions. Civilian semi-automatic variants are common in the US; fully automatic versions are heavily regulated under the NFA.; Also known as: AK, AK-47, AK47, AK-74; See also: Semi-automatic, NFA (National Firearms Act)
Ankle carryLegal and Carry: Ankle holsters strap a small revolver or subcompact to the non-dominant leg's ankle. They conceal well under long pants and are a common backup position for plainclothes officers. Very slow to access, and only suitable for genuinely small guns.; See also: Concealed carry
Appendix carry (AIWB)Legal and Carry: AIWB places the holster at the front of the waist. It enables the fastest presentation of any carry position and conceals extremely well under a tucked shirt. Requires disciplined re-holstering: the muzzle sweeps the femoral area if you're careless.; Also known as: AIWB; See also: Inside the waistband (IWB), Concealed carry
AR-15Action Types: The AR-15 is a gas-operated, magazine-fed semi-automatic rifle designed by Eugene Stoner in the 1950s. The civilian AR-15 fires one round per trigger pull. Modular design means barrels, handguards, triggers, and stocks can be swapped easily. Most common chambering is 5.56mm NATO / .223 Remington.; Also known as: AR, AR15; See also: Semi-automatic, NATO round (5.56 NATO / 7.62 NATO), Bolt carrier group (BCG)
ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives)Legal and Carry: The ATF enforces federal firearm laws, licenses dealers (FFLs), processes NFA registrations and tax stamps, runs the tracing program, and investigates firearm-related federal crimes. Rule changes from the ATF can materially affect what is lawful to build, own, or sell.; Also known as: ATF, BATFE; See also: NFA (National Firearms Act), Federal Firearms License (FFL), NICS background check

B

Ball-and-dummy drillMarksmanship: A partner (or blind loading) mixes dummy rounds into the magazine. When a dummy reaches the chamber, any flinch shows dramatically as the gun dips. One of the single most effective diagnostic drills in pistol training.; See also: Flinch, Snap cap
Ballistic tipAmmunition: Ballistic tip bullets combine a hollow cavity with a pointed polymer tip. The tip keeps the nose profile consistent for smooth feeding, improves aerodynamic efficiency, and initiates expansion on impact. Common in hunting and long-range rifle ammunition.; See also: Hollow point (HP / JHP)
BarrelFirearm Parts: The barrel is the tube that directs the bullet out of the firearm. Rifling (spiral grooves) inside the bore imparts spin for stability. Barrel length influences velocity and handling, and the bore diameter determines caliber or gauge.; See also: Bore, rifling, Caliber
Barrel crownFirearm Parts: The crown is the final point of contact between the bullet and the barrel. Any nick or unevenness disturbs the bullet's exit and degrades accuracy. Always clean rifles from the breech toward the muzzle to protect the crown.; Also known as: crown, muzzle crown; See also: Barrel, muzzle
Battery (in/out of battery)Action Types: A gun is 'in battery' when the bolt or slide is fully forward and locked against the chamber. Firing 'out of battery' (before full lockup) can rupture the case and injure the shooter. Most designs physically prevent this, but worn parts or forced closures bypass that protection.; See also: Headspace
BirdshotAmmunition: Birdshot is a shotgun load of many small pellets (sizes 7, 8, 9, etc.). It is effective for hunting birds and breaking clay targets, but lacks the penetration needed for reliable self-defense against a human attacker.; See also: Shotgun shell, Buckshot
Boat tailAmmunition: Boat-tail bullets have a slightly tapered rear profile that reduces base drag, flattening trajectory at long range. Standard on precision rifle and match ammunition. Slightly heavier and more expensive than flat-base bullets of equivalent weight.; See also: Ogive
Bolt carrier group (BCG)Firearm Parts: The BCG rides the upper receiver's rails and cycles with every shot, locking and unlocking the bolt to extract, eject, and chamber rounds. Fouling of the BCG is a leading cause of AR malfunctions, so it is the primary cleaning focus.; Also known as: BCG, carrier; See also: Bolt-action, Charging handle, Gas key
Bolt lugsFirearm Parts: Bolt lugs are the primary lockup mechanism on bolt-action and many semi-automatic rifles. As the action closes, the lugs rotate or slide into place to hold the bolt against chamber pressure. Excessive lug wear causes headspace problems.; Also known as: locking lugs; See also: Bolt-action, Headspace
Bolt-actionAction Types: Bolt-action rifles require the shooter to manually operate a bolt handle to eject a spent case and chamber the next round. The simplicity of the action makes them inherently reliable and accurate, which is why they dominate hunting and precision shooting.; See also: Semi-automatic
BoreFirearm Parts: The bore is the hollow interior of the barrel. Its internal diameter and rifling pattern are precision-machined for a specific cartridge. Keeping the bore clean and unobstructed is critical to safe function.; See also: Barrel, Caliber, Gauge, rifling
Bore sightOptics and Sights: Bore sighting is a first-pass alignment that gets your first shot on paper. It does not replace zeroing, which must be confirmed with live fire. Many ranges and retailers offer free bore-sighting.; Also known as: boresight; See also: Zero / zeroing
Bottleneck cartridgeAmmunition: Bottleneck designs let the case hold more powder behind a smaller bullet, enabling high velocities. Almost all modern rifle cartridges are bottleneck. The opposite design is straight-wall (most pistol and some lever-action rifle cartridges).; See also: Case neck, Case shoulder
Break-actionAction Types: Break-action firearms pivot the barrel open on a hinge pin. They include single-shot rifles, double-barrel shotguns, and derringers. Simple and reliable, but slow to reload: each round is inserted manually into the chamber.; Also known as: hinge-action; See also: Pump-action, Revolver
Breath controlMarksmanship: The standard technique is to inhale, exhale halfway, hold briefly, and press. If the shot isn't ready within a few seconds, breathe again rather than holding to the point of oxygen debt (which introduces tremor).; See also: Follow-through, Natural point of aim (NPA)
BreechFirearm Parts: The breech is where barrel and bolt meet to seal the chamber during firing. The breech face is the flat surface on the bolt or slide that the firing pin protrudes through. Damage here is dangerous and indicates the firearm needs gunsmithing.; Also known as: breech face; See also: Headspace, Barrel
BuckshotAmmunition: Buckshot is a shotgun load of several large lead or tungsten pellets. 00 ('double-ought') buck is the classic defensive load: typically 8-9 pellets of roughly .33-inch diameter per shell. It delivers significant energy and spreads over distance.; See also: Shotgun shell, Birdshot
BulletAmmunition: The bullet is the metal projectile seated at the front of a cartridge. It is what actually flies downrange; the case, powder, and primer stay behind. Bullet weight is measured in grains (gr).; See also: Cartridge, Grain (gr)
Bullet drop compensation (BDC)Optics and Sights: BDC reticles place additional stadia lines, dots, or rings below the main aiming point. Each corresponds to the bullet's drop at a named distance for a specific load. Useful for fast shots in the field; less flexible than a mil-grid reticle.; Also known as: BDC; See also: Reticle, Holdover

C

CaliberAmmunition: Caliber refers to the inside diameter of a barrel, which determines what cartridge it fires. Notation is inconsistent by history: .22 LR is 0.22 inch, 9mm is 9 millimeter, and .38 Special is actually ~0.357 inch. When in doubt, match the cartridge name stamped on the gun.; See also: Bore, Cartridge, Gauge
Call the shotMarksmanship: Calling your shot means saying (to yourself or an instructor) where the sights were as the trigger broke. Over time this trains awareness of the true sight picture and separates aiming errors from trigger errors.; See also: Sight picture, Follow-through
CartridgeAmmunition: A cartridge (or 'round') is the complete ammunition unit: a metal case containing propellant powder, sealed at the base by a primer, with a bullet seated at the front. When people say 'bullet' they usually mean the whole cartridge, but the bullet is only the projectile.; Also known as: round, ammunition, ammo; See also: Bullet, Primer, Case (cartridge case), Caliber
Case (cartridge case)Ammunition: The cartridge case holds the components together and seals the chamber against gas escape when fired. Brass is the standard because it expands and re-seals the chamber, then contracts for easy extraction. Reloaders save their brass; steel and aluminum cases are usually not reloadable.; Also known as: brass, casing; See also: Cartridge, brass
Case neckAmmunition: On bottleneck rifle cases the neck is the slim section that holds the bullet in place. Neck tension (how firmly it grips) is a critical reloading variable. Neck splits are a common fatigue sign in older brass.; Also known as: case-neck; See also: Case shoulder, Bottleneck cartridge
Case rimAmmunition: The rim is the flat flange at the head of the case. Rimmed cartridges have a clearly larger rim (.22 LR, .38 Special); rimless cartridges have a rim the same diameter as the body with an extractor groove cut into it.; See also: Extractor
Case shoulderAmmunition: The shoulder is the sloped section where the case narrows from body to neck. On most modern rifle cartridges the shoulder datum (a specific point on the slope) is what headspaces the cartridge in the chamber.; See also: Case neck, Headspace
Castle doctrineLegal and Carry: Castle doctrine laws vary by state. Where adopted, a person inside their own home (and sometimes vehicle or workplace) generally has no legal duty to retreat before using lawful force against an unlawful intruder. Oregon's use-of-force law is governed by ORS 161.209-161.219 and does not include a formal castle doctrine; consult an attorney for specifics.; See also: Stand your ground, Duty to retreat
Cease-fireSafety and Handling: A cease-fire is a range safety command. When called, every shooter must stop firing, remove their finger from the trigger, safely unload, show clear, and step back from the line before anyone goes downrange.; See also: Cold range, Show clear
CenterfireAmmunition: Centerfire cartridges use a separate primer pressed into a pocket at the center of the case head. This design tolerates much higher pressures than rimfire, enables reloading, and supports essentially all modern rifle and defensive handgun calibers.; See also: Rimfire, Primer
ChamberFirearm Parts: The chamber is the part of the barrel cut to hold and support a specific cartridge during firing. A revolver has multiple chambers in its cylinder; most other firearms have a single chamber at the rear of the barrel.; See also: Barrel, Cartridge, Headspace
Charging handleFirearm Parts: The charging handle is the shooter's manual interface to the bolt carrier group. Pulling it back cycles the action without firing, used to chamber the first round and to clear malfunctions. On AR-pattern rifles it sits at the rear of the upper receiver.; Also known as: charge handle, cocking handle; See also: Bolt carrier group (BCG)
ChokeAmmunition: A shotgun choke tightens the muzzle and shapes the shot pattern. Cylinder is no constriction (widest spread); Improved Cylinder, Modified, and Full are progressively tighter. Most modern shotguns use screw-in choke tubes that let you change constriction for the task.; See also: Pattern (shot pattern)
ClipFirearm Parts: A clip is a loading device: cartridges are held on the clip, which is then inserted or stripped into the firearm's fixed magazine. Many people use 'clip' to mean 'magazine,' but they are mechanically different.; See also: Magazine
Co-witnessOptics and Sights: Co-witnessing lets you aim with the iron sights through the red-dot window if the electronic sight fails. Absolute co-witness places the irons on the dot; lower-1/3 co-witness places the dot above the irons for faster presentation.; Also known as: co-witness; See also: Absolute co-witness, Lower 1/3 co-witness, Red dot (RDS)
Cold rangeSafety and Handling: A 'cold' range is the state where no one may load, handle, or point a firearm because people are downrange (changing or repairing targets) or the range officer has called a cease-fire. A 'hot' range is the opposite: firearms may be handled at your shooting position only.; See also: Cease-fire, range-commands
Concealed carryLegal and Carry: Concealed carry is carrying a firearm so that it is not visible to casual observation. Most states require a permit (such as the Oregon CHL), though a minority allow permitless or 'constitutional' carry. Concealment depends on holster, garment, and body mechanics.; Also known as: CCW; See also: Concealed Handgun License (CHL), Open carry
Concealed Handgun License (CHL)Legal and Carry: A Concealed Handgun License is a state license that allows the holder to carry a concealed handgun. Names differ by state (CCW, CPL, CHP, CHL). Oregon issues CHLs through the county sheriff's office and requires a training course, background check, and fingerprinting.; Also known as: CCW, CPL, concealed carry permit; See also: Open carry, Constitutional carry
Constitutional carryLegal and Carry: Constitutional carry (or permitless carry) lets eligible adults carry concealed without a state permit. As of 2025, roughly half of U.S. states have some form of it. Oregon is not one of them: an Oregon CHL is required to carry concealed in the state.; Also known as: permitless carry; See also: Concealed Handgun License (CHL), Concealed carry
Controlled pairMarksmanship: A controlled pair is NOT a 'double tap' thrown from recoil memory. Each shot has its own sight picture and trigger press. At typical defensive distances shooters can run controlled pairs very fast without sacrificing accuracy.; Also known as: double tap; See also: Transition
Cross-dominantMarksmanship: About a third of people are cross-dominant. Workarounds include closing the dominant eye, canting the head slightly, or switching shooting hands for precision rifle work. Red dot sights reduce the disadvantage dramatically.; See also: Dominant eye

D

180-degree ruleSafety and Handling: The 180 is an invisible line across the firing line. Everything that happens with a firearm must keep the muzzle pointed downrange of that line. Turning to talk to a neighbor with a gun in hand is the classic violation. Ranges enforce this strictly.; See also: Four Rules of Firearm Safety, Muzzle discipline
Dominant eyeMarksmanship: To find your dominant eye: make a triangle with your hands at arm's length, focus on a distant object through the hole, then bring your hands slowly to your face. The hole lines up with your dominant eye. Most shooting uses that eye regardless of hand dominance.; Also known as: master eye; See also: Cross-dominant
Double-action (DA / DAO / DA/SA)Action Types: A double-action trigger both cocks and releases the hammer on each press. DAO (double-action only) keeps every shot a heavy press. DA/SA fires the first shot double-action, then single-action for the rest. Revolvers are commonly DAO or DA/SA capable.; Also known as: DA, DAO, DA/SA, double action; See also: Single-action (SA / SAO), Striker-fired
Draw strokeMarksmanship: The draw stroke is a reproducible series of positions: establish grip, clear leather, rotate, join, extend, press. Dry-fire training the draw stroke with an unloaded firearm builds reliable speed and keeps the finger off the trigger until the sights are aligned.; See also: Presentation
Drop safetySafety and Handling: Drop safeties physically block the firing pin or disconnect the trigger unless the trigger is deliberately pressed. Modern striker-fired pistols typically have multiple internal safeties layered to meet drop-test standards. Older firearms may lack drop safeties entirely.; See also: Firing pin, Safety (mechanical)
Dry fireMarksmanship: Dry fire is practicing firearm fundamentals with an unloaded gun. It builds trigger control, draw, and sight skills at zero ammunition cost. The #1 safety rule: treat dry-fire as its own range session — ammo out of the room, verify clear, use a safe backstop anyway.; See also: Trigger press, Four Rules of Firearm Safety
Duty holsterLegal and Carry: Duty holsters include one or more active retention devices (hood, thumb lever, rotating lock). Security is rated Level I (friction only) through Level III+ (multiple active mechanisms). Intended for OWB carry and regular weapon-retention training.; See also: Retention level, Outside the waistband (OWB)
Duty to retreatLegal and Carry: Duty-to-retreat jurisdictions require that a person who can safely retreat from a threat do so before resorting to deadly force. Oregon case law considers retreat as one factor in the necessity analysis but does not impose a strict duty. This is a critical area to understand with local legal guidance.; See also: Castle doctrine, Stand your ground

E

EjectorFirearm Parts: After the extractor pulls the spent case from the chamber, the ejector strikes or pushes it out through the ejection port. A worn or damaged ejector causes cases to dribble out instead of clearing cleanly.; See also: Extractor
Elevation turretOptics and Sights: The elevation turret moves the reticle up and down to compensate for bullet drop at distance. One click typically equals 1/4 MOA or 0.1 mil. Many match scopes have precision 'exposed' turrets for rapid dial-up.; See also: Windage turret, Minute of Angle (MOA), Milliradian (MIL / MRAD)
Elevator (shell lifter)Firearm Parts: The elevator is a movable tray inside a pump shotgun's receiver. As the forend cycles, the elevator rises to align the next shell with the chamber. Fouling under the elevator causes feeding issues.; Also known as: shell lifter; See also: Pump-action
Exit pupilOptics and Sights: Exit pupil equals the objective lens diameter divided by magnification. A 50mm objective at 10x produces a 5mm exit pupil. In low light your pupil dilates to 5 to 7mm, so a larger exit pupil delivers a brighter image.; See also: Eye box
ExtractorFirearm Parts: The extractor is a small claw or hook on the bolt or slide that engages the rim of a spent cartridge case and pulls it from the chamber as the action cycles. Weak or broken extractors are a common cause of stovepipe and failure-to-eject malfunctions.; See also: Ejector, Case rim
Eye boxOptics and Sights: The eye box is the volume behind the scope where both eye relief and centering line up. A large eye box is forgiving to sloppy head position; a small one demands precise mounting. High-magnification scopes tend to have tighter eye boxes.; See also: Eye relief, Exit pupil
Eye protection (eye pro)Range and Gear: Shooting eye protection must be ANSI Z87.1 or MIL-PRF-32432 rated. It shields against ejected brass, powder flash, debris from ricochets, and the (rare) catastrophic firearm failure. FST provides both standard and over-glasses styles.; Also known as: eyepro, shooting glasses; See also: Hearing protection (ear pro)
Eye reliefOptics and Sights: Eye relief is the safe gap between scope and eye. Magnified scopes typically need 3 to 4 inches; red dots are eye-relief-independent. Too little relief risks the scope striking your brow under recoil ('scope bite').; See also: Eye box

F

Federal Firearms License (FFL)Legal and Carry: An FFL holder is the regulated intermediary for interstate firearm sales. When you buy a gun online, it ships to a local FFL who performs the NICS background check and transfers it to you in person.; See also: NICS background check
Feed rampFirearm Parts: The feed ramp is a polished, angled section at the base of the chamber. Cartridges stripped from the magazine ride up the ramp and into the chamber. Rough or dirty ramps cause failure-to-feed, especially with hollow-point ammunition.; See also: Magazine, Chamber
Fiber optic sightOptics and Sights: Fiber optic sights use a sliver of fluorescent plastic fiber to collect ambient light and pipe it to the shooter's eye, producing a vivid dot in daylight. They need no batteries but go dark in true low light (where tritium takes over).; See also: Tritium, Iron sights
Firing pinFirearm Parts: The firing pin is driven forward by the hammer or striker and dents the cartridge's primer, which ignites the powder. On many modern pistols the striker IS the firing pin.; See also: Hammer, Primer, Striker-fired
Firing pin channelFirearm Parts: The firing pin channel is a small bore inside the bolt or breech-block. Carbon and oil accumulate here and can slow the firing pin, causing light primer strikes. Regular cleaning with a dedicated brush keeps it functioning reliably.; See also: Firing pin, Light primer strike
First focal plane (FFP)Optics and Sights: In an FFP scope the reticle is etched in front of the zoom lens, so it grows and shrinks with magnification. Subtension marks stay accurate at every power, which is ideal for shooters using the reticle for holdovers and ranging.; Also known as: first focal plane; See also: Second focal plane (SFP), Scope (rifle scope)
FlinchMarksmanship: Flinching is the most common source of misses for newer shooters. The fix is mental (learn to welcome recoil) and mechanical (smooth trigger press, ball-and-dummy drills). It cannot be out-muscled; it must be trained away.; Also known as: anticipation; See also: Ball-and-dummy drill, Trigger press
Follow-throughMarksmanship: Follow-through is holding position and sight focus through recoil and until the gun settles. It prevents the last-instant movements that throw shots. Practically: keep the trigger pinned, re-acquire the sights, and reset only after the gun has come back to zero.; See also: Call the shot, Trigger reset
Forcing coneFirearm Parts: The forcing cone guides bullets from the cylinder chambers into the barrel bore on revolvers. Carbon and lead foul this area heavily; neglected forcing cones erode and hurt accuracy. Regular scrubbing is essential revolver maintenance.; See also: Revolver, cylinder
Four Rules of Firearm SafetySafety and Handling: Jeff Cooper's four universal rules of firearm safety are layered defenses: each one alone prevents a tragedy even if others fail. They apply regardless of whether you believe the firearm is unloaded. Internalizing them is the foundation of all further training.; Also known as: 4 rules, safety rules; See also: Trigger discipline, Muzzle discipline
FrameFirearm Parts: The frame (also called the receiver on long guns) is the housing that holds the action, grip, and other components. It is typically the serial-numbered, legally regulated part of the firearm.; See also: Receiver, Slide
FrangibleAmmunition: Frangible bullets are compressed metal powder bonded together. On impact with a hard target they break into tiny fragments instead of ricocheting or over-penetrating. Popular for steel-target training and some confined-space applications.; See also: Hollow point (HP / JHP)
Full metal jacket (FMJ)Ammunition: FMJ bullets have a lead core fully enclosed in a copper jacket. They are cheaper to produce, feed reliably, and don't expand, making them ideal for range practice. FMJ is generally a poor choice for self-defense because it over-penetrates.; See also: Hollow point (HP / JHP)

G

Gas keyFirearm Parts: The gas key is a small rectangular fitting bolted to the top of the AR-15 bolt carrier. It channels gas from the gas tube into the carrier to drive cycling. Carbon around the gas key is a common cause of short-stroking on dirty rifles.; See also: Bolt carrier group (BCG), Gas-operated
Gas-operatedAction Types: Gas-operated actions bleed expanding propellant gas from a port in the barrel into a piston or directly onto the bolt carrier, driving it rearward to cycle. Produces less felt recoil than recoil-operated designs but requires more cleaning.; Also known as: direct impingement, piston-operated; See also: Semi-automatic, Inertia-driven, Gas key
GaugeAmmunition: Gauge is a historical shotgun bore-size system: the number of lead balls of bore diameter that weigh one pound. So 12 gauge means 12 balls to the pound, and is physically larger than 20 gauge. The .410 bore is an exception, named by actual inches, not gauge.; See also: Bore, Shotgun shell
Ghost ring sightOptics and Sights: Ghost ring sights are rear apertures large enough that the rim blurs when you focus on the front post. Your eye naturally centers the post in the ring, making them fast and intuitive. Common on combat shotguns and some defensive rifles.; Also known as: peep sight; See also: Iron sights
Grain (gr)Ammunition: A grain is a small mass unit (about 65 mg). Bullet weights are given in grains: a 115-grain 9mm is lighter and faster than a 147-grain 9mm. Powder charges and arrow weights are also measured in grains.; See also: Bullet
GripMarksmanship: Pistol grip technique is high on the backstrap, firm but not death-crushing, with the support hand wrapped around the shooting hand and thumbs forward. A good grip controls recoil and produces consistent trigger-finger placement.; See also: Stance, Recoil
Group (shot group)Marksmanship: A tight group means consistent technique; a scattered group means something is varying shot-to-shot. Group location tells you about zero (the offset from point of aim). Read both together to diagnose yourself and your gun.; Also known as: grouping; See also: Zero / zeroing, Call the shot

H

HammerFirearm Parts: The hammer swings forward under spring pressure when the trigger is pressed, striking the firing pin which in turn strikes the primer. Modern striker-fired pistols use a striker instead.; See also: Striker-fired, Firing pin
Hammer spring (mainspring)Firearm Parts: The mainspring is usually a coil or leaf spring that powers the hammer. A weak mainspring causes light primer strikes and misfires. On revolvers the mainspring also affects trigger feel.; Also known as: mainspring; See also: Hammer, Light primer strike
Handload / reloadAmmunition: Handloading is the practice of assembling cartridges on a reloading press. It saves money, tailors accuracy, and provides access to cartridges that are scarce. It also requires training, attention, and meticulous process control: mistakes produce squibs, overpressure, or worse.; Also known as: reload, reloading, handloading; See also: Squib (squib load)
HangfireAmmunition: A hangfire is a perceptible delay (usually fractions of a second to a couple of seconds) between the primer strike and the powder burn. Rare with modern ammunition. If you suspect a hangfire, keep the muzzle pointed downrange for at least 30 seconds before opening the action.; See also: Squib (squib load), Light primer strike
HeadspaceAction Types: Headspace is measured with precision gauges and ensures the cartridge sits at exactly the right depth when the bolt is locked. Excessive headspace allows dangerous rearward gas leakage; insufficient headspace prevents the action from closing. This is gunsmith-level measurement.; Also known as: headspacing; See also: Chamber, Breech
Hearing protection (ear pro)Range and Gear: Gunfire is loud enough to cause permanent hearing damage from a single shot. Hearing protection is measured in NRR (Noise Reduction Rating). Electronic 'active' muffs amplify speech while blocking gunshots. Indoor ranges often warrant 'doubling up' (plugs under muffs).; Also known as: earpro, muffs, earplugs; See also: Eye protection (eye pro)
HeelingMarksmanship: Heeling is a form of recoil anticipation where the dominant palm pushes forward. Shots print high and sometimes strong-side. Fix with surprise-break trigger practice and conscious grip relaxation.; See also: Flinch
High readyMarksmanship: High ready is quicker in close quarters and reduces muzzle sweep of people below you. It is slower to present than low ready at arm's length but more protective in a crowd.; See also: Low ready, Sul position
HoldoffOptics and Sights: Holdoff is the horizontal equivalent of holdover. In a stiff crosswind you aim into the wind by a known number of mils or MOA to place the bullet on target. Faster than turret dialing under field conditions.; See also: Holdover
HoldoverOptics and Sights: Holdover uses reticle marks (or estimated offsets) to place shots at different ranges without touching the turrets. Faster than dialing, but demands a reticle calibrated to your ammunition. Common with BDC reticles or mil/moa grids.; See also: Bullet drop compensation (BDC), Holdoff
Hollow point (HP / JHP)Ammunition: Hollow-point bullets have a hollow cavity in the nose. On impact with soft tissue they expand (mushroom), creating a larger wound channel and dumping more energy in the target. They are the standard for self-defense because expansion reduces over-penetration. Jacketed Hollow Point (JHP) adds a copper jacket for reliable feeding.; Also known as: JHP, hollowpoint; See also: Full metal jacket (FMJ), ballistics
HolsterRange and Gear: A quality holster is firearm-specific, fully covers the trigger guard, retains the firearm through normal movement, and re-holsters without the help of the support hand. Materials include Kydex (rigid), leather, and hybrids. Fit the holster to the gun AND to your carry position (IWB, OWB, appendix).; See also: Concealed carry, Trigger discipline
HullAmmunition: The hull is the tube of a shotgun shell. Modern hulls are almost always plastic; paper hulls persist for classic side-by-side gunning. Hulls can be reloaded several times before the mouth frays too badly to crimp.; See also: Shotgun shell, Wad

I

IFAK (Individual First Aid Kit)Range and Gear: An IFAK is a focused bleeding-control kit carried at the range or in the vehicle. Minimum contents: CAT tourniquet, pressure dressing (Israeli/OLAES), hemostatic gauze (QuikClot/Celox), chest seal, gloves, trauma shears. Keep it reachable, not buried in a bag.; Also known as: IFAK, trauma kit; See also: Tourniquet
Illuminated reticleOptics and Sights: Illuminated reticles keep the aiming reference visible against dark targets or at dawn/dusk. LED illumination offers adjustable brightness but needs batteries; tritium glows continuously for years without power.; See also: Tritium, Reticle
Inertia-drivenAction Types: Inertia-driven actions rely on the shooter's body absorbing recoil while a spring-loaded bolt stays briefly stationary relative to the rearward-moving gun, then snaps back to cycle. Simpler and cleaner than gas-operated designs but pickier about light loads.; Also known as: recoil-operated; See also: Gas-operated
Inside the waistband (IWB)Legal and Carry: IWB carry rides between body and waistband, with a clip or loop attaching to the belt. It conceals better than OWB and adapts to many body types. Comfort depends heavily on the belt, holster fit, and pant sizing.; Also known as: IWB; See also: Outside the waistband (OWB), Appendix carry (AIWB)
Iron sightsOptics and Sights: Iron sights are the original sighting system: a front post or bead and a rear notch or peep. They are rugged, always-on, and require no batteries. Most new shooters start with iron sights, and they remain essential as a backup to electronic optics.; See also: Red dot (RDS), Sight picture
Isosceles stanceMarksmanship: Isosceles is named for the triangle formed by chest and extended arms. Body-armor-friendly, symmetric, and strong against recoil, it has largely supplanted the older bladed Weaver stance for defensive pistol work.; See also: Weaver stance, Stance

L

Light primer strikeAmmunition: A light primer strike is a shallow dent on the primer with no ignition. Common causes include fouling in the firing pin channel, weak mainspring, or excess oil damping pin travel. Cleaning and proper lubrication usually fix it.; Also known as: light strike; See also: Firing pin channel, Hammer spring (mainspring)
Loaded chamber indicator (LCI)Safety and Handling: LCIs range from a peek-through hole to a raised tab that protrudes when a round is in battery. They help under poor light or stress, but good training teaches a visual-and-tactile chamber check regardless of what the indicator says.; Also known as: LCI; See also: Four Rules of Firearm Safety
Low readyMarksmanship: Low ready keeps the muzzle safely downrange, lets you see the target and hands clearly, and supports a fast push-up to the sights. It's the default ready position for most defensive training.; See also: High ready, Sul position
Lower 1/3 co-witnessOptics and Sights: Lower-1/3 co-witness puts the red dot higher above the bore, so the irons only appear when you deliberately look for them. Favored on carbines for a cleaner primary sight picture with the iron sights available as backup.; See also: Co-witness, Absolute co-witness

M

M-LOKOptics and Sights: M-LOK (Modular Lock) is a Magpul-developed mounting standard that uses slots instead of a full rail profile. Lighter and slimmer than Picatinny, it has largely replaced KeyMod as the dominant accessory mount on modern carbines.; Also known as: mlok; See also: Picatinny rail
MagazineFirearm Parts: A magazine holds cartridges in a stack and feeds them one at a time as the action cycles. It is distinct from a clip (which is a loading device). Capacity limits vary by state law.; Also known as: mag; See also: Clip, Cartridge
Mantis X10 EliteRange and Gear: The Mantis X10 Elite is a motion-sensor training aid that mounts to a firearm and records micro-movements during each trigger press. It pairs with an app to diagnose flinch, anticipation, and grip issues. FST uses the X10 to give data-driven feedback during training.; See also: Dry fire, Trigger press
MilkingMarksmanship: Milking is the instinct for the whole hand to squeeze together on the trigger pull. The result is an irregular grip at the moment of ignition. Cured by isolated trigger-finger practice during dry fire.; See also: Trigger press, Grip
Milliradian (MIL / MRAD)Marksmanship: A milliradian (mil) is 1/1000 of a radian. Most modern tactical and military scopes use mils for both reticle subtensions and turret adjustments, which makes range estimation math cleaner in metric units.; Also known as: MRAD, mildot; See also: Minute of Angle (MOA), Zero / zeroing
Minute of Angle (MOA)Marksmanship: Minute of Angle is 1/60 of a degree. At 100 yards, 1 MOA is approximately 1.047 inches. Scope adjustments are often in fractions of MOA (e.g. 1/4 MOA per click), and rifle accuracy is often rated in MOA (a 'sub-MOA rifle' shoots groups smaller than 1 inch at 100 yards).; Also known as: minute of angle; See also: Milliradian (MIL / MRAD), Zero / zeroing
Muzzle disciplineSafety and Handling: Muzzle discipline is the habitual awareness of the direction your barrel is pointed at all times — loaded or unloaded, in your hand or holstered. It is the physical expression of Rules 1 and 2 of the four rules.; See also: Four Rules of Firearm Safety, Trigger discipline

N

NATO round (5.56 NATO / 7.62 NATO)Ammunition: NATO cartridges are standardized for interoperability among member nations. 5.56 NATO is dimensionally similar to .223 Remington but loaded to higher pressure (check your rifle's chamber marking). 7.62 NATO is dimensionally similar to .308 Winchester with similar pressure caveats.; Also known as: NATO, 5.56 NATO, 7.62 NATO; See also: Caliber, AR-15
Natural point of aim (NPA)Marksmanship: Natural point of aim is where the firearm settles when your muscles relax. If your NPA is off the target you'll fight it with every shot, costing accuracy and stamina. Finding NPA is a matter of shifting your whole body (not your arms) until the gun points at the target when relaxed.; Also known as: NPA; See also: Stance, Breath control
Negligent discharge (ND)Safety and Handling: A negligent discharge is any unintended firing of a firearm. The term 'negligent' (rather than 'accidental') reflects that nearly every ND traces back to a human violation of the four rules, most often trigger discipline or a failure to verify the gun was unloaded.; Also known as: ND, accidental discharge, AD; See also: Four Rules of Firearm Safety, Trigger discipline
NFA (National Firearms Act)Legal and Carry: The National Firearms Act imposes registration, a $200 tax stamp, and ATF approval for transfers of NFA items: short-barreled rifles (SBRs), short-barreled shotguns (SBSs), suppressors, machine guns, Any Other Weapons (AOWs), and destructive devices. Requirements apply at both purchase and interstate travel with NFA items.; Also known as: NFA; See also: SBR (Short-Barreled Rifle), Suppressor (silencer), ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives)
NICS background checkLegal and Carry: NICS is the federal background check system run by the FBI. Federally licensed firearm dealers (FFLs) must run a NICS check on buyers before a firearm transfer. Oregon adds a state requirement on top: a background check for private-party transfers too, not just dealer sales. Oregon does not have a mandatory waiting period.; Also known as: background check; See also: Federal Firearms License (FFL)
NIJ ratingRange and Gear: NIJ ratings certify body armor against specific threat levels. IIA-IIIA are soft panels rated for handgun rounds. Level III stops common rifle rounds (7.62x51 FMJ); Level IV stops armor-piercing rifle rounds. Always match armor to realistic threats and understand its limits.; Also known as: NIJ; See also: soft-armor
NRA (National Rifle Association)Legal and Carry: The NRA is the oldest civil-rights organization in the United States. Its training division certifies instructors and publishes well-known beginner curricula. Some communities prefer alternative training organizations; FST offers LGBTQIA+-focused instruction that is independent of the NRA.; Also known as: NRA

O

OgiveAmmunition: The ogive is the tapered section between the bullet's shoulder and tip. Sharp ogives slip through the air better at range; blunt ogives feed more reliably in certain actions. Competition shooters measure overall length to a specific ogive point for consistency.; See also: Bullet, Boat tail
Open carryLegal and Carry: Open carry is the practice of carrying a visible firearm in public. It is legal in much of the United States, but many cities and private properties restrict or prohibit it. In Oregon, open carry is generally legal but some cities (like Portland) have additional restrictions in public buildings and parks.; See also: Concealed Handgun License (CHL), Concealed carry
Outside the waistband (OWB)Legal and Carry: OWB carry is standard for duty, range, and open carry. It is typically more comfortable than IWB for extended periods but requires longer cover garments to conceal. Better access for shooters with mobility constraints.; Also known as: OWB; See also: Inside the waistband (IWB), Open carry
Over-grippingMarksmanship: A too-hard grip produces shake and makes the trigger press ragged. Aim for consistent, repeatable pressure rather than maximum force. Many instructors call this the '7/10 rule' — firm enough to control recoil, relaxed enough to hold steady.; Also known as: death grip; See also: Grip

P

+PAmmunition: +P rounds are loaded to higher SAAMI-approved pressures for more velocity and energy, at the cost of increased recoil and accelerated wear. Always verify the firearm is +P-rated before routine use; many older designs are not.; Also known as: plus-p; See also: +P+
+P+Ammunition: +P+ is an informal designation for loads beyond SAAMI +P pressures, typically produced for law enforcement or specific platforms. Without an industry-wide standard, only use +P+ in firearms explicitly approved for it.; Also known as: plus-p-plus; See also: +P
ParallaxOptics and Sights: Parallax happens when the reticle and target images are not at the same optical plane. You notice it when the reticle seems to drift across the target as you move your head. Many scopes have a parallax adjustment (often a side knob) to remove it at a given distance.; See also: Scope (rifle scope), First focal plane (FFP), Second focal plane (SFP)
Pattern (shot pattern)Ammunition: Patterning your shotgun means firing a given load at 30 or 40 yards and measuring how many pellets fall inside a 30-inch circle. Every barrel, choke, and load combination produces a different pattern. Patterning is mandatory before relying on a shotgun for defense or hunting.; See also: Choke, Shotgun shell
Penny drillMarksmanship: The penny drill is a self-diagnostic for trigger control. Balance a coin on the front sight (or the slide), press through in dry fire, and see whether the coin survives. It's cheap, silent, and humbling.; See also: Trigger jerk, Dry fire
Picatinny railOptics and Sights: Picatinny rails are the universal mounting interface on most modern firearms. The numbered cross-slots let optics clamp securely and return to the same position after removal. Don't confuse with the similar-looking Weaver rail (different slot spacing).; Also known as: pic rail; See also: M-LOK
Prep the triggerMarksmanship: Prepping the trigger means applying partial pressure to remove pre-travel while the sights are still settling. When the sights are right, a minimal additional press breaks the shot cleanly. Used in precision and competition shooting; not a beginner habit.; See also: Trigger staging, Trigger press
PresentationMarksmanship: A clean presentation grips the gun in the holster, clears, rotates to the target, joins hands, and extends out to full sight picture in one continuous motion. Consistency beats speed; smooth becomes fast with repetition.; See also: Draw stroke, Sight picture
PrimerAmmunition: The primer is a small metal cup filled with shock-sensitive compound, seated into the base of a cartridge case. The firing pin strikes it, it ignites the powder, and the powder's rapid burn launches the bullet. Primers are either 'boxer' or 'berdan' style; boxer is standard in the US.; See also: Firing pin, Cartridge
PrintingLegal and Carry: Printing happens when a garment is too tight or thin, or when you move in ways that pull cloth against the gun. It reveals you're armed to anyone looking. Proper garment cut, holster geometry, and movement awareness prevent it.; See also: Concealed carry, Appendix carry (AIWB)
Pump-actionAction Types: Pump-action is the dominant shotgun action type. The shooter pulls the forend rearward to eject the spent shell, then pushes it forward to chamber the next. Pump guns are extremely reliable because the shooter provides all cycling energy.; Also known as: slide-action; See also: Break-action, Semi-automatic

R

Ready positionMarksmanship: Ready positions balance safety, awareness, and speed to first shot. Choice depends on distance, environment, and the number of targets. Training should include transitions from each ready position to the target.; See also: Low ready, High ready, Sul position
ReceiverFirearm Parts: The receiver is the long-gun equivalent of a pistol frame: the central metal body that holds the bolt, trigger group, and other working parts. On AR-pattern rifles it is split into an upper (barrel/bolt) and lower (trigger/stock) receiver.; See also: Frame, Bolt-action
RecoilMarksmanship: Recoil is the rearward momentum the shooter feels when a round fires — Newton's third law at work. Felt recoil depends on cartridge power, firearm weight, action type, and shooter technique. Proper grip and stance manage recoil and keep follow-up shots fast.; Also known as: kick; See also: Stance, Grip
Recoil springFirearm Parts: The recoil spring stores energy when the slide cycles rearward and returns the slide forward to chamber the next round. A tired recoil spring causes short-stroking and feeding failures. Replacement every 3,000 to 5,000 rounds is a common interval.; Also known as: return spring; See also: Slide, Bolt carrier group (BCG)
Red dot (RDS)Optics and Sights: A red dot sight projects an LED dot onto a lens in the shooter's line of sight. You focus on the target, place the dot, and press. It removes the need to align front and rear sights, is fast, and works well with both eyes open. Common on pistols, rifles, and shotguns.; Also known as: RDS, reflex sight; See also: Iron sights, Minute of Angle (MOA), Zero / zeroing
Red flag law (ERPO)Legal and Carry: Red flag laws (Extreme Risk Protection Orders) are civil procedures where family members, household members, or law enforcement can petition a court to temporarily suspend someone's firearm rights. Oregon has an ERPO statute (ORS 166.525-166.543). Subject to due-process requirements including a hearing.; Also known as: ERPO, Extreme Risk Protection Order
Retention levelLegal and Carry: Retention levels count active locks beyond passive friction. Level I is friction only, Level II adds one active lock, Level III adds a second, and so on. Higher retention defeats weapon grabs better but slows down the draw.; See also: Duty holster
ReticleOptics and Sights: The reticle is the aiming reference visible through a scope or red dot. Designs range from simple crosshairs to Christmas-tree reticles with wind and drop holds. Reticle choice should match the shooter's intended distance and lighting.; Also known as: crosshair, crosshairs; See also: Scope (rifle scope), Bullet drop compensation (BDC)
RevolverAction Types: A revolver stores rounds in a rotating cylinder rather than a magazine. Pressing the trigger (double-action) or cocking the hammer (single-action) indexes the cylinder to line up the next chamber with the barrel. Revolvers are mechanically simple and very reliable.; See also: Chamber, Double-action (DA / DAO / DA/SA)
Rifled slugAmmunition: Rifled slugs (also called Foster slugs) have angled grooves on the outside. The grooves do not spin the slug; they let it safely pass through shotgun chokes. Rifled slugs stabilize aerodynamically and are designed for smoothbore shotgun barrels.; See also: Slug, Sabot slug, Smoothbore
RimfireAmmunition: In a rimfire cartridge the priming compound is spun into the folded rim of the case. The firing pin crushes the rim against the chamber edge to ignite. Rimfire is cheap and low-recoil, making it ideal for training, but low-powered and not reloadable.; See also: Centerfire, Primer

S

Sabot slugAmmunition: Sabot slugs use a plastic sleeve to engage the rifling in a dedicated slug barrel. The sleeve separates downrange, leaving the slug spinning for stability. Effective range can exceed 150 yards. Requires a rifled shotgun barrel, not a smoothbore.; See also: Slug, Rifled slug
Safety (mechanical)Firearm Parts: A mechanical safety physically blocks some part of the firing chain when engaged. Types include manual thumb safeties, grip safeties, trigger safeties, and drop safeties. Mechanical safeties can fail and are never a replacement for the four rules of firearm safety.; See also: Four Rules of Firearm Safety
SBR (Short-Barreled Rifle)Legal and Carry: Federal law defines an SBR as a rifle with a barrel shorter than 16 inches or total length shorter than 26 inches. Ownership requires NFA registration, a $200 tax stamp, and ATF approval. Crossing state lines with an SBR requires prior ATF notification via Form 5320.20.; Also known as: SBR; See also: NFA (National Firearms Act), ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives)
SBS (Short-Barreled Shotgun)Legal and Carry: SBSs carry the same NFA registration, tax stamp, and approval requirements as SBRs. Barrel length and overall length are both measured; either under the limit triggers NFA regulation.; Also known as: SBS; See also: NFA (National Firearms Act), SBR (Short-Barreled Rifle)
Scope (rifle scope)Optics and Sights: A rifle scope uses lenses to magnify the target and provides a reticle for aiming. Modern scopes offer variable magnification, illuminated reticles, and precise turret adjustments. Selection depends on the rifle's role (hunting, precision, close-range).; See also: Minute of Angle (MOA), Milliradian (MIL / MRAD), Zero / zeroing
Second focal plane (SFP)Optics and Sights: SFP scopes keep the reticle visually constant while the image around it zooms. Simpler and cheaper than FFP, but holdover marks are calibrated for a specific magnification (usually max). Most hunting scopes are SFP.; Also known as: second focal plane, rear focal plane; See also: First focal plane (FFP)
Semi-automaticAction Types: A semi-automatic firearm uses energy from firing (recoil or tapped gas) to eject the spent case and chamber a new round. One press of the trigger fires one shot. This is the dominant modern design for pistols and many rifles.; Also known as: semi-auto, autoloader; See also: Slide, Bolt-action
Short-strokingAction Types: Short-stroking is a shooter error on pump guns: the forend is not pulled far enough back or pushed far enough forward. The fix is simple but counterintuitive under stress: cycle the action with authority, all the way back and all the way forward.; See also: Pump-action
Shotgun shellAmmunition: Shotgun shells use a plastic hull with a brass base. Birdshot and buckshot loads contain many pellets; slug loads contain a single projectile. The shell is usually crimped at the end, and fires from a smoothbore barrel (with exceptions for rifled slug barrels).; Also known as: shell, shotshell; See also: Gauge, Buckshot, Birdshot, Slug
Show clearSafety and Handling: Showing clear means removing any source of ammunition (magazine), cycling or locking the action open, and presenting the chamber for visual verification. It is the standard way to prove a firearm is safe before handing it off, storing it, or stepping away from the line.; See also: Cease-fire, Four Rules of Firearm Safety
Sight alignmentMarksmanship: Sight alignment refers only to the relationship of the front and rear sights to each other: front centered in the rear notch, equal light gaps on either side of the front post, and tops level. Sight picture adds the target to this equation.; See also: Sight picture
Sight pictureMarksmanship: Sight picture is the complete view through your sights when everything is aligned: front sight focused and level with the rear, centered in the notch, held on the desired point on the target. For most handgun shooting the front sight is in sharp focus while the target is slightly blurry.; See also: Sight alignment, Trigger press
Single-action (SA / SAO)Action Types: A single-action trigger performs one job: releasing an already-cocked hammer or striker. The pull is typically short and light. 1911-pattern pistols are classic examples; they must be carried cocked-and-locked or manually cocked before the first shot.; Also known as: SA, SAO, single action only; See also: Double-action (DA / DAO / DA/SA), Striker-fired
SlideFirearm Parts: On a semi-automatic pistol, the slide cycles rearward under recoil, ejects the spent case, and strips a new cartridge from the magazine on its return. It houses the barrel, extractor, and firing pin or striker.; See also: Semi-automatic, Striker-fired, Recoil
Slide railsFirearm Parts: Slide rails are precision-machined tracks on the frame. Good lubrication here is critical to reliable cycling. Dry or gritty rails cause sluggish slide action and malfunctions.; Also known as: rails; See also: Slide, Frame
SlugAmmunition: Shotgun slugs are single solid projectiles, typically 7/8 to 1-1/4 ounces. They hit far harder than any pistol round but require more aim than buckshot. Rifled slugs work in smoothbore barrels; sabot slugs work in rifled shotgun barrels.; See also: Rifled slug, Sabot slug, Smoothbore
SmoothboreAmmunition: Most shotgun barrels are smoothbore: the bore is a smooth tube with no spiral grooves. Pellets and rifled slugs work here. Sabot slugs require a rifled barrel. Smoothbores are cheaper, simpler, and easier to clean than rifled barrels.; See also: Rifled slug, Sabot slug
Snap capMarksmanship: Snap caps let you cycle, dry-fire, and practice malfunction drills without using live rounds and without dry-firing on an empty chamber (which can stress firing pins in rimfire and some older designs).; Also known as: dummy round; See also: Dry fire, Ball-and-dummy drill
Soft point (SP)Ammunition: Soft points have a jacketed body with lead exposed at the tip. On impact the lead mushrooms and expands the projectile. They are a hunting mainstay and feed more reliably than some hollow-point designs in older actions.; See also: Hollow point (HP / JHP), Full metal jacket (FMJ)
Squib (squib load)Ammunition: A squib is usually signaled by a muffled 'pop,' negligible recoil, and no bullet impact downrange. Firing another round behind a lodged bullet WILL rupture the barrel. If you suspect a squib, stop, unload, and check the bore with a cleaning rod before firing again.; See also: Hangfire, Light primer strike
StanceMarksmanship: A good shooting stance is athletic and stable: feet shoulder-width, slight forward lean, weight balanced toward the balls of the feet. Isosceles (square to target) is the modern standard; Weaver (bladed) is an older alternative. Stance manages recoil and supports consistent follow-up shots.; See also: Grip, Recoil
Stand your groundLegal and Carry: Stand-your-ground laws extend castle doctrine concepts to places outside the home where the person is lawfully present. Oregon is NOT a stand-your-ground state. Oregon's use-of-force standard requires that force be 'necessary' and proportional; consult a lawyer for specifics.; See also: Castle doctrine, Duty to retreat
Straw purchaseLegal and Carry: A straw purchase is when a qualified buyer purchases a firearm for an unqualified buyer or to hide the true owner. Lying on ATF Form 4473 about this is a federal felony (up to 10 years). Gift purchases between legal buyers are NOT straw purchases as long as the giver is the true purchaser.; See also: Federal Firearms License (FFL), NICS background check
Striker-firedAction Types: Striker-fired pistols use a partially pre-tensioned internal striker rather than an external hammer. The trigger pull finishes cocking and then releases the striker. Designs are typically simple, with consistent trigger pulls and no manual de-cocking.; See also: Hammer, Single-action (SA / SAO), Double-action (DA / DAO / DA/SA)
SubsonicAmmunition: Subsonic loads use heavier bullets and reduced powder to keep the bullet below supersonic speed, eliminating the sonic crack. Combined with a suppressor, subsonic fire is genuinely quiet. Trade-off is reduced energy and range.; See also: Supersonic
Sul positionMarksmanship: Sul (Portuguese for 'south') is a close-quarters carry position where the muzzle points at the ground along the body's centerline. It keeps the muzzle off bystanders and teammates while allowing fast presentation.; Also known as: sul; See also: Low ready, High ready
SupersonicAmmunition: Most factory ammunition is supersonic. The bullet breaks the sound barrier on the way downrange and produces a crack that is audible regardless of suppressor use. Supersonic loads deliver full-power energy and range.; See also: Subsonic
Support handMarksmanship: The support hand should do most of the gripping work, freeing the trigger hand to operate the trigger smoothly. Modern technique places the support thumb forward and the palm high on the grip for maximum recoil control.; Also known as: weak hand; See also: Grip
Suppressor (silencer)Range and Gear: Suppressors don't make firearms movie-quiet — they reduce peak noise from around 160 dB to 130-140 dB, comparable to a jackhammer. They help preserve hearing and reduce recoil and muzzle flash. Federally regulated under the NFA: $200 tax stamp, ATF approval, registered ownership.; Also known as: silencer; See also: NFA (National Firearms Act), Subsonic
Surprise breakMarksmanship: A surprise break is the goal of pure trigger control: you apply steady pressure while holding the sight picture, and the shot 'just happens.' If you can predict the exact instant the gun will fire you will flinch. Dry-fire practice trains this.; See also: Flinch, Trigger press

T

Takedown pinFirearm Parts: Takedown pins are cylindrical pins (one or two, depending on design) that let you separate major assemblies for cleaning. On AR-15s the takedown and pivot pins separate upper and lower receivers; on many pistols a single takedown lever releases the slide.; Also known as: pivot pin; See also: field-strip
Target acquisitionMarksmanship: Target acquisition is the chain from 'see' to 'sights on target.' Training speeds this process through drilling the draw, transitions, and sight pick-up. Before firing, acquisition must include target identification and what lies behind it.; See also: Presentation, Transition
ThumbingMarksmanship: Thumbing comes from tight dominant-thumb pressure. Typical cure: adopt a high thumbs-forward grip with both thumbs off the frame, pointed toward the target.; See also: Grip
TourniquetRange and Gear: A tourniquet is the first-line treatment for massive limb bleeding from firearm injuries. Apply 2-3 inches above the wound, tighten until bleeding stops, note the time. Only CAT (Combat Application Tourniquet) and SOFTT-W are considered field-proven. Improvised tourniquets are a last resort.; See also: IFAK (Individual First Aid Kit)
TransitionMarksmanship: Transitioning between targets efficiently means snapping your eyes to the next target first, then driving the gun to follow your vision. Good transitions control the recoil of the previous shot so the gun arrives ready to fire again.; See also: Controlled pair, Target acquisition
TriggerFirearm Parts: The trigger is the lever that releases the hammer or striker to fire the cartridge. Trigger 'pull weight' (force required) and 'travel' (distance) are key feel characteristics and vary across single-action, double-action, and striker-fired designs.; See also: Single-action (SA / SAO), Double-action (DA / DAO / DA/SA), Striker-fired, Trigger discipline
Trigger disciplineSafety and Handling: Trigger discipline means the finger stays indexed along the frame (outside the trigger guard) except at the moment of firing. It is the physical expression of Rule 3 of the four rules and prevents the vast majority of negligent discharges.; See also: Four Rules of Firearm Safety, Negligent discharge (ND)
Trigger jerkMarksmanship: Trigger jerk is a discrete, fast pull. It disturbs sight alignment before the shot breaks. Dry fire with a coin balanced on the front sight is a classic diagnostic: the coin falls if you jerk.; See also: Trigger press, Penny drill
Trigger pressMarksmanship: A controlled, straight-to-the-rear trigger press is the foundation of accuracy. Most new-shooter misses come not from aim but from jerking or anticipating. Dry-fire practice builds this skill more efficiently than live fire.; Also known as: trigger pull, trigger squeeze; See also: Sight picture, Dry fire
Trigger resetMarksmanship: Most modern pistols have a short reset: you let the trigger travel forward just enough to hear/feel a click, then press again. Riding the reset produces faster, more consistent follow-up shots than fully releasing the trigger.; Also known as: reset; See also: Trigger press, Controlled pair
Trigger stagingMarksmanship: Staging is most useful on long, heavy double-action pulls. The shooter walks the trigger to the break, holds while finalizing the sight picture, and then breaks with minimal additional motion. Not typically used with striker-fired pistols.; See also: Double-action (DA / DAO / DA/SA), Prep the trigger
TritiumOptics and Sights: Tritium is a hydrogen isotope that emits light as it decays (half-life ~12 years). Encapsulated in small vials it lights up iron sights and some reticles without batteries. The dose is tiny and shielded by the sight body.; See also: Illuminated reticle, Iron sights

U

USCCA (U.S. Concealed Carry Association)Legal and Carry: The USCCA provides concealed-carry training materials and a membership that includes self-defense legal protection coverage (attorney fees and civil liability). A common pick for people who carry concealed; alternatives include Second Call Defense and CCW Safe.; Also known as: USCCA; See also: Concealed carry, Concealed Handgun License (CHL)

W

WadAmmunition: The wad cups the pellets together inside the hull and seals against the barrel as the shot accelerates. Once clear of the muzzle it falls away from the shot column. Wads are often recovered downrange.; See also: Shotgun shell, Hull
WadcutterAmmunition: Wadcutters have a flat or slightly concave nose that cuts crisp holes in paper, which helps scoring in bullseye competition. Not suited for semi-auto feeding or defensive use, but excellent for revolvers at the target range.; See also: Full metal jacket (FMJ)
Weaver stanceMarksmanship: Weaver places the support-side foot forward, angles the body to the target, and creates push-pull tension with a bent trigger arm and straight support arm. Still taught historically, but isosceles dominates modern defensive pistol training.; See also: Isosceles stance, Stance
Windage turretOptics and Sights: The windage turret moves the reticle left and right. Windage adjustments are most commonly used for cross-winds at range. Like elevation, calibrated in MOA or mil clicks.; See also: Elevation turret

Z

Zero / zeroingMarksmanship: To zero a firearm is to adjust its sights or scope so that where you aim is where it hits at a given distance. Common handgun zeros are 25 yards; rifle zeros vary by purpose (50-yard, 100-yard, or 36-yard 'battle zero' for 5.56mm).; Also known as: zeroing, sight-in; See also: Minute of Angle (MOA), Sight picture

Question about a term?

Glossaries are easier to remember with a real firearm in your hands. Come shoot with us.

Book a Familiarization

Firearms Glossary

Plain-language definitions of the terminology you will encounter in our classes, at the range, and online. New terms are added as our content grows.

By Category

Action Types

AK platform (AK-47 / AK-74)
AR-15
Battery (in/out of battery)
Bolt-action
Break-action
Double-action (DA / DAO / DA/SA)
Gas-operated
Headspace
Inertia-driven
Pump-action
Revolver
Semi-automatic
Short-stroking
Single-action (SA / SAO)
Striker-fired

Range and Gear

Eye protection (eye pro)
Hearing protection (ear pro)
Holster
IFAK (Individual First Aid Kit)
Mantis X10 Elite
NIJ rating
Suppressor (silencer)
Tourniquet

A to Z

A

Absolute co-witnessOptics and Sights: At absolute co-witness the iron sights and the red dot superimpose exactly. This yields a clean backup sight picture if the dot dies, at the cost of the irons cluttering the lower half of the optic window.; See also: Co-witness, Lower 1/3 co-witness
ActionFirearm Parts: The action is the working heart of the firearm: the set of parts that chamber a round, fire it, and extract and eject the spent case. Action type (bolt, lever, pump, semi-automatic, etc.) determines how the gun cycles and how fast it can be fired.; See also: Bolt-action, Semi-automatic, Striker-fired
AK platform (AK-47 / AK-74)Action Types: The AK platform is a long-stroke gas-piston rifle system developed by Mikhail Kalashnikov in 1947. It is famous for reliability under harsh conditions. Civilian semi-automatic variants are common in the US; fully automatic versions are heavily regulated under the NFA.; Also known as: AK, AK-47, AK47, AK-74; See also: Semi-automatic, NFA (National Firearms Act)
Ankle carryLegal and Carry: Ankle holsters strap a small revolver or subcompact to the non-dominant leg's ankle. They conceal well under long pants and are a common backup position for plainclothes officers. Very slow to access, and only suitable for genuinely small guns.; See also: Concealed carry
Appendix carry (AIWB)Legal and Carry: AIWB places the holster at the front of the waist. It enables the fastest presentation of any carry position and conceals extremely well under a tucked shirt. Requires disciplined re-holstering: the muzzle sweeps the femoral area if you're careless.; Also known as: AIWB; See also: Inside the waistband (IWB), Concealed carry
AR-15Action Types: The AR-15 is a gas-operated, magazine-fed semi-automatic rifle designed by Eugene Stoner in the 1950s. The civilian AR-15 fires one round per trigger pull. Modular design means barrels, handguards, triggers, and stocks can be swapped easily. Most common chambering is 5.56mm NATO / .223 Remington.; Also known as: AR, AR15; See also: Semi-automatic, NATO round (5.56 NATO / 7.62 NATO), Bolt carrier group (BCG)
ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives)Legal and Carry: The ATF enforces federal firearm laws, licenses dealers (FFLs), processes NFA registrations and tax stamps, runs the tracing program, and investigates firearm-related federal crimes. Rule changes from the ATF can materially affect what is lawful to build, own, or sell.; Also known as: ATF, BATFE; See also: NFA (National Firearms Act), Federal Firearms License (FFL), NICS background check

B

Ball-and-dummy drillMarksmanship: A partner (or blind loading) mixes dummy rounds into the magazine. When a dummy reaches the chamber, any flinch shows dramatically as the gun dips. One of the single most effective diagnostic drills in pistol training.; See also: Flinch, Snap cap
Ballistic tipAmmunition: Ballistic tip bullets combine a hollow cavity with a pointed polymer tip. The tip keeps the nose profile consistent for smooth feeding, improves aerodynamic efficiency, and initiates expansion on impact. Common in hunting and long-range rifle ammunition.; See also: Hollow point (HP / JHP)
BarrelFirearm Parts: The barrel is the tube that directs the bullet out of the firearm. Rifling (spiral grooves) inside the bore imparts spin for stability. Barrel length influences velocity and handling, and the bore diameter determines caliber or gauge.; See also: Bore, rifling, Caliber
Barrel crownFirearm Parts: The crown is the final point of contact between the bullet and the barrel. Any nick or unevenness disturbs the bullet's exit and degrades accuracy. Always clean rifles from the breech toward the muzzle to protect the crown.; Also known as: crown, muzzle crown; See also: Barrel, muzzle
Battery (in/out of battery)Action Types: A gun is 'in battery' when the bolt or slide is fully forward and locked against the chamber. Firing 'out of battery' (before full lockup) can rupture the case and injure the shooter. Most designs physically prevent this, but worn parts or forced closures bypass that protection.; See also: Headspace
BirdshotAmmunition: Birdshot is a shotgun load of many small pellets (sizes 7, 8, 9, etc.). It is effective for hunting birds and breaking clay targets, but lacks the penetration needed for reliable self-defense against a human attacker.; See also: Shotgun shell, Buckshot
Boat tailAmmunition: Boat-tail bullets have a slightly tapered rear profile that reduces base drag, flattening trajectory at long range. Standard on precision rifle and match ammunition. Slightly heavier and more expensive than flat-base bullets of equivalent weight.; See also: Ogive
Bolt carrier group (BCG)Firearm Parts: The BCG rides the upper receiver's rails and cycles with every shot, locking and unlocking the bolt to extract, eject, and chamber rounds. Fouling of the BCG is a leading cause of AR malfunctions, so it is the primary cleaning focus.; Also known as: BCG, carrier; See also: Bolt-action, Charging handle, Gas key
Bolt lugsFirearm Parts: Bolt lugs are the primary lockup mechanism on bolt-action and many semi-automatic rifles. As the action closes, the lugs rotate or slide into place to hold the bolt against chamber pressure. Excessive lug wear causes headspace problems.; Also known as: locking lugs; See also: Bolt-action, Headspace
Bolt-actionAction Types: Bolt-action rifles require the shooter to manually operate a bolt handle to eject a spent case and chamber the next round. The simplicity of the action makes them inherently reliable and accurate, which is why they dominate hunting and precision shooting.; See also: Semi-automatic
BoreFirearm Parts: The bore is the hollow interior of the barrel. Its internal diameter and rifling pattern are precision-machined for a specific cartridge. Keeping the bore clean and unobstructed is critical to safe function.; See also: Barrel, Caliber, Gauge, rifling
Bore sightOptics and Sights: Bore sighting is a first-pass alignment that gets your first shot on paper. It does not replace zeroing, which must be confirmed with live fire. Many ranges and retailers offer free bore-sighting.; Also known as: boresight; See also: Zero / zeroing
Bottleneck cartridgeAmmunition: Bottleneck designs let the case hold more powder behind a smaller bullet, enabling high velocities. Almost all modern rifle cartridges are bottleneck. The opposite design is straight-wall (most pistol and some lever-action rifle cartridges).; See also: Case neck, Case shoulder
Break-actionAction Types: Break-action firearms pivot the barrel open on a hinge pin. They include single-shot rifles, double-barrel shotguns, and derringers. Simple and reliable, but slow to reload: each round is inserted manually into the chamber.; Also known as: hinge-action; See also: Pump-action, Revolver
Breath controlMarksmanship: The standard technique is to inhale, exhale halfway, hold briefly, and press. If the shot isn't ready within a few seconds, breathe again rather than holding to the point of oxygen debt (which introduces tremor).; See also: Follow-through, Natural point of aim (NPA)
BreechFirearm Parts: The breech is where barrel and bolt meet to seal the chamber during firing. The breech face is the flat surface on the bolt or slide that the firing pin protrudes through. Damage here is dangerous and indicates the firearm needs gunsmithing.; Also known as: breech face; See also: Headspace, Barrel
BuckshotAmmunition: Buckshot is a shotgun load of several large lead or tungsten pellets. 00 ('double-ought') buck is the classic defensive load: typically 8-9 pellets of roughly .33-inch diameter per shell. It delivers significant energy and spreads over distance.; See also: Shotgun shell, Birdshot
BulletAmmunition: The bullet is the metal projectile seated at the front of a cartridge. It is what actually flies downrange; the case, powder, and primer stay behind. Bullet weight is measured in grains (gr).; See also: Cartridge, Grain (gr)
Bullet drop compensation (BDC)Optics and Sights: BDC reticles place additional stadia lines, dots, or rings below the main aiming point. Each corresponds to the bullet's drop at a named distance for a specific load. Useful for fast shots in the field; less flexible than a mil-grid reticle.; Also known as: BDC; See also: Reticle, Holdover

C

CaliberAmmunition: Caliber refers to the inside diameter of a barrel, which determines what cartridge it fires. Notation is inconsistent by history: .22 LR is 0.22 inch, 9mm is 9 millimeter, and .38 Special is actually ~0.357 inch. When in doubt, match the cartridge name stamped on the gun.; See also: Bore, Cartridge, Gauge
Call the shotMarksmanship: Calling your shot means saying (to yourself or an instructor) where the sights were as the trigger broke. Over time this trains awareness of the true sight picture and separates aiming errors from trigger errors.; See also: Sight picture, Follow-through
CartridgeAmmunition: A cartridge (or 'round') is the complete ammunition unit: a metal case containing propellant powder, sealed at the base by a primer, with a bullet seated at the front. When people say 'bullet' they usually mean the whole cartridge, but the bullet is only the projectile.; Also known as: round, ammunition, ammo; See also: Bullet, Primer, Case (cartridge case), Caliber
Case (cartridge case)Ammunition: The cartridge case holds the components together and seals the chamber against gas escape when fired. Brass is the standard because it expands and re-seals the chamber, then contracts for easy extraction. Reloaders save their brass; steel and aluminum cases are usually not reloadable.; Also known as: brass, casing; See also: Cartridge, brass
Case neckAmmunition: On bottleneck rifle cases the neck is the slim section that holds the bullet in place. Neck tension (how firmly it grips) is a critical reloading variable. Neck splits are a common fatigue sign in older brass.; Also known as: case-neck; See also: Case shoulder, Bottleneck cartridge
Case rimAmmunition: The rim is the flat flange at the head of the case. Rimmed cartridges have a clearly larger rim (.22 LR, .38 Special); rimless cartridges have a rim the same diameter as the body with an extractor groove cut into it.; See also: Extractor
Case shoulderAmmunition: The shoulder is the sloped section where the case narrows from body to neck. On most modern rifle cartridges the shoulder datum (a specific point on the slope) is what headspaces the cartridge in the chamber.; See also: Case neck, Headspace
Castle doctrineLegal and Carry: Castle doctrine laws vary by state. Where adopted, a person inside their own home (and sometimes vehicle or workplace) generally has no legal duty to retreat before using lawful force against an unlawful intruder. Oregon's use-of-force law is governed by ORS 161.209-161.219 and does not include a formal castle doctrine; consult an attorney for specifics.; See also: Stand your ground, Duty to retreat
Cease-fireSafety and Handling: A cease-fire is a range safety command. When called, every shooter must stop firing, remove their finger from the trigger, safely unload, show clear, and step back from the line before anyone goes downrange.; See also: Cold range, Show clear
CenterfireAmmunition: Centerfire cartridges use a separate primer pressed into a pocket at the center of the case head. This design tolerates much higher pressures than rimfire, enables reloading, and supports essentially all modern rifle and defensive handgun calibers.; See also: Rimfire, Primer
ChamberFirearm Parts: The chamber is the part of the barrel cut to hold and support a specific cartridge during firing. A revolver has multiple chambers in its cylinder; most other firearms have a single chamber at the rear of the barrel.; See also: Barrel, Cartridge, Headspace
Charging handleFirearm Parts: The charging handle is the shooter's manual interface to the bolt carrier group. Pulling it back cycles the action without firing, used to chamber the first round and to clear malfunctions. On AR-pattern rifles it sits at the rear of the upper receiver.; Also known as: charge handle, cocking handle; See also: Bolt carrier group (BCG)
ChokeAmmunition: A shotgun choke tightens the muzzle and shapes the shot pattern. Cylinder is no constriction (widest spread); Improved Cylinder, Modified, and Full are progressively tighter. Most modern shotguns use screw-in choke tubes that let you change constriction for the task.; See also: Pattern (shot pattern)
ClipFirearm Parts: A clip is a loading device: cartridges are held on the clip, which is then inserted or stripped into the firearm's fixed magazine. Many people use 'clip' to mean 'magazine,' but they are mechanically different.; See also: Magazine
Co-witnessOptics and Sights: Co-witnessing lets you aim with the iron sights through the red-dot window if the electronic sight fails. Absolute co-witness places the irons on the dot; lower-1/3 co-witness places the dot above the irons for faster presentation.; Also known as: co-witness; See also: Absolute co-witness, Lower 1/3 co-witness, Red dot (RDS)
Cold rangeSafety and Handling: A 'cold' range is the state where no one may load, handle, or point a firearm because people are downrange (changing or repairing targets) or the range officer has called a cease-fire. A 'hot' range is the opposite: firearms may be handled at your shooting position only.; See also: Cease-fire, range-commands
Concealed carryLegal and Carry: Concealed carry is carrying a firearm so that it is not visible to casual observation. Most states require a permit (such as the Oregon CHL), though a minority allow permitless or 'constitutional' carry. Concealment depends on holster, garment, and body mechanics.; Also known as: CCW; See also: Concealed Handgun License (CHL), Open carry
Concealed Handgun License (CHL)Legal and Carry: A Concealed Handgun License is a state license that allows the holder to carry a concealed handgun. Names differ by state (CCW, CPL, CHP, CHL). Oregon issues CHLs through the county sheriff's office and requires a training course, background check, and fingerprinting.; Also known as: CCW, CPL, concealed carry permit; See also: Open carry, Constitutional carry
Constitutional carryLegal and Carry: Constitutional carry (or permitless carry) lets eligible adults carry concealed without a state permit. As of 2025, roughly half of U.S. states have some form of it. Oregon is not one of them: an Oregon CHL is required to carry concealed in the state.; Also known as: permitless carry; See also: Concealed Handgun License (CHL), Concealed carry
Controlled pairMarksmanship: A controlled pair is NOT a 'double tap' thrown from recoil memory. Each shot has its own sight picture and trigger press. At typical defensive distances shooters can run controlled pairs very fast without sacrificing accuracy.; Also known as: double tap; See also: Transition
Cross-dominantMarksmanship: About a third of people are cross-dominant. Workarounds include closing the dominant eye, canting the head slightly, or switching shooting hands for precision rifle work. Red dot sights reduce the disadvantage dramatically.; See also: Dominant eye

D

180-degree ruleSafety and Handling: The 180 is an invisible line across the firing line. Everything that happens with a firearm must keep the muzzle pointed downrange of that line. Turning to talk to a neighbor with a gun in hand is the classic violation. Ranges enforce this strictly.; See also: Four Rules of Firearm Safety, Muzzle discipline
Dominant eyeMarksmanship: To find your dominant eye: make a triangle with your hands at arm's length, focus on a distant object through the hole, then bring your hands slowly to your face. The hole lines up with your dominant eye. Most shooting uses that eye regardless of hand dominance.; Also known as: master eye; See also: Cross-dominant
Double-action (DA / DAO / DA/SA)Action Types: A double-action trigger both cocks and releases the hammer on each press. DAO (double-action only) keeps every shot a heavy press. DA/SA fires the first shot double-action, then single-action for the rest. Revolvers are commonly DAO or DA/SA capable.; Also known as: DA, DAO, DA/SA, double action; See also: Single-action (SA / SAO), Striker-fired
Draw strokeMarksmanship: The draw stroke is a reproducible series of positions: establish grip, clear leather, rotate, join, extend, press. Dry-fire training the draw stroke with an unloaded firearm builds reliable speed and keeps the finger off the trigger until the sights are aligned.; See also: Presentation
Drop safetySafety and Handling: Drop safeties physically block the firing pin or disconnect the trigger unless the trigger is deliberately pressed. Modern striker-fired pistols typically have multiple internal safeties layered to meet drop-test standards. Older firearms may lack drop safeties entirely.; See also: Firing pin, Safety (mechanical)
Dry fireMarksmanship: Dry fire is practicing firearm fundamentals with an unloaded gun. It builds trigger control, draw, and sight skills at zero ammunition cost. The #1 safety rule: treat dry-fire as its own range session — ammo out of the room, verify clear, use a safe backstop anyway.; See also: Trigger press, Four Rules of Firearm Safety
Duty holsterLegal and Carry: Duty holsters include one or more active retention devices (hood, thumb lever, rotating lock). Security is rated Level I (friction only) through Level III+ (multiple active mechanisms). Intended for OWB carry and regular weapon-retention training.; See also: Retention level, Outside the waistband (OWB)
Duty to retreatLegal and Carry: Duty-to-retreat jurisdictions require that a person who can safely retreat from a threat do so before resorting to deadly force. Oregon case law considers retreat as one factor in the necessity analysis but does not impose a strict duty. This is a critical area to understand with local legal guidance.; See also: Castle doctrine, Stand your ground

E

EjectorFirearm Parts: After the extractor pulls the spent case from the chamber, the ejector strikes or pushes it out through the ejection port. A worn or damaged ejector causes cases to dribble out instead of clearing cleanly.; See also: Extractor
Elevation turretOptics and Sights: The elevation turret moves the reticle up and down to compensate for bullet drop at distance. One click typically equals 1/4 MOA or 0.1 mil. Many match scopes have precision 'exposed' turrets for rapid dial-up.; See also: Windage turret, Minute of Angle (MOA), Milliradian (MIL / MRAD)
Elevator (shell lifter)Firearm Parts: The elevator is a movable tray inside a pump shotgun's receiver. As the forend cycles, the elevator rises to align the next shell with the chamber. Fouling under the elevator causes feeding issues.; Also known as: shell lifter; See also: Pump-action
Exit pupilOptics and Sights: Exit pupil equals the objective lens diameter divided by magnification. A 50mm objective at 10x produces a 5mm exit pupil. In low light your pupil dilates to 5 to 7mm, so a larger exit pupil delivers a brighter image.; See also: Eye box
ExtractorFirearm Parts: The extractor is a small claw or hook on the bolt or slide that engages the rim of a spent cartridge case and pulls it from the chamber as the action cycles. Weak or broken extractors are a common cause of stovepipe and failure-to-eject malfunctions.; See also: Ejector, Case rim
Eye boxOptics and Sights: The eye box is the volume behind the scope where both eye relief and centering line up. A large eye box is forgiving to sloppy head position; a small one demands precise mounting. High-magnification scopes tend to have tighter eye boxes.; See also: Eye relief, Exit pupil
Eye protection (eye pro)Range and Gear: Shooting eye protection must be ANSI Z87.1 or MIL-PRF-32432 rated. It shields against ejected brass, powder flash, debris from ricochets, and the (rare) catastrophic firearm failure. FST provides both standard and over-glasses styles.; Also known as: eyepro, shooting glasses; See also: Hearing protection (ear pro)
Eye reliefOptics and Sights: Eye relief is the safe gap between scope and eye. Magnified scopes typically need 3 to 4 inches; red dots are eye-relief-independent. Too little relief risks the scope striking your brow under recoil ('scope bite').; See also: Eye box

F

Federal Firearms License (FFL)Legal and Carry: An FFL holder is the regulated intermediary for interstate firearm sales. When you buy a gun online, it ships to a local FFL who performs the NICS background check and transfers it to you in person.; See also: NICS background check
Feed rampFirearm Parts: The feed ramp is a polished, angled section at the base of the chamber. Cartridges stripped from the magazine ride up the ramp and into the chamber. Rough or dirty ramps cause failure-to-feed, especially with hollow-point ammunition.; See also: Magazine, Chamber
Fiber optic sightOptics and Sights: Fiber optic sights use a sliver of fluorescent plastic fiber to collect ambient light and pipe it to the shooter's eye, producing a vivid dot in daylight. They need no batteries but go dark in true low light (where tritium takes over).; See also: Tritium, Iron sights
Firing pinFirearm Parts: The firing pin is driven forward by the hammer or striker and dents the cartridge's primer, which ignites the powder. On many modern pistols the striker IS the firing pin.; See also: Hammer, Primer, Striker-fired
Firing pin channelFirearm Parts: The firing pin channel is a small bore inside the bolt or breech-block. Carbon and oil accumulate here and can slow the firing pin, causing light primer strikes. Regular cleaning with a dedicated brush keeps it functioning reliably.; See also: Firing pin, Light primer strike
First focal plane (FFP)Optics and Sights: In an FFP scope the reticle is etched in front of the zoom lens, so it grows and shrinks with magnification. Subtension marks stay accurate at every power, which is ideal for shooters using the reticle for holdovers and ranging.; Also known as: first focal plane; See also: Second focal plane (SFP), Scope (rifle scope)
FlinchMarksmanship: Flinching is the most common source of misses for newer shooters. The fix is mental (learn to welcome recoil) and mechanical (smooth trigger press, ball-and-dummy drills). It cannot be out-muscled; it must be trained away.; Also known as: anticipation; See also: Ball-and-dummy drill, Trigger press
Follow-throughMarksmanship: Follow-through is holding position and sight focus through recoil and until the gun settles. It prevents the last-instant movements that throw shots. Practically: keep the trigger pinned, re-acquire the sights, and reset only after the gun has come back to zero.; See also: Call the shot, Trigger reset
Forcing coneFirearm Parts: The forcing cone guides bullets from the cylinder chambers into the barrel bore on revolvers. Carbon and lead foul this area heavily; neglected forcing cones erode and hurt accuracy. Regular scrubbing is essential revolver maintenance.; See also: Revolver, cylinder
Four Rules of Firearm SafetySafety and Handling: Jeff Cooper's four universal rules of firearm safety are layered defenses: each one alone prevents a tragedy even if others fail. They apply regardless of whether you believe the firearm is unloaded. Internalizing them is the foundation of all further training.; Also known as: 4 rules, safety rules; See also: Trigger discipline, Muzzle discipline
FrameFirearm Parts: The frame (also called the receiver on long guns) is the housing that holds the action, grip, and other components. It is typically the serial-numbered, legally regulated part of the firearm.; See also: Receiver, Slide
FrangibleAmmunition: Frangible bullets are compressed metal powder bonded together. On impact with a hard target they break into tiny fragments instead of ricocheting or over-penetrating. Popular for steel-target training and some confined-space applications.; See also: Hollow point (HP / JHP)
Full metal jacket (FMJ)Ammunition: FMJ bullets have a lead core fully enclosed in a copper jacket. They are cheaper to produce, feed reliably, and don't expand, making them ideal for range practice. FMJ is generally a poor choice for self-defense because it over-penetrates.; See also: Hollow point (HP / JHP)

G

Gas keyFirearm Parts: The gas key is a small rectangular fitting bolted to the top of the AR-15 bolt carrier. It channels gas from the gas tube into the carrier to drive cycling. Carbon around the gas key is a common cause of short-stroking on dirty rifles.; See also: Bolt carrier group (BCG), Gas-operated
Gas-operatedAction Types: Gas-operated actions bleed expanding propellant gas from a port in the barrel into a piston or directly onto the bolt carrier, driving it rearward to cycle. Produces less felt recoil than recoil-operated designs but requires more cleaning.; Also known as: direct impingement, piston-operated; See also: Semi-automatic, Inertia-driven, Gas key
GaugeAmmunition: Gauge is a historical shotgun bore-size system: the number of lead balls of bore diameter that weigh one pound. So 12 gauge means 12 balls to the pound, and is physically larger than 20 gauge. The .410 bore is an exception, named by actual inches, not gauge.; See also: Bore, Shotgun shell
Ghost ring sightOptics and Sights: Ghost ring sights are rear apertures large enough that the rim blurs when you focus on the front post. Your eye naturally centers the post in the ring, making them fast and intuitive. Common on combat shotguns and some defensive rifles.; Also known as: peep sight; See also: Iron sights
Grain (gr)Ammunition: A grain is a small mass unit (about 65 mg). Bullet weights are given in grains: a 115-grain 9mm is lighter and faster than a 147-grain 9mm. Powder charges and arrow weights are also measured in grains.; See also: Bullet
GripMarksmanship: Pistol grip technique is high on the backstrap, firm but not death-crushing, with the support hand wrapped around the shooting hand and thumbs forward. A good grip controls recoil and produces consistent trigger-finger placement.; See also: Stance, Recoil
Group (shot group)Marksmanship: A tight group means consistent technique; a scattered group means something is varying shot-to-shot. Group location tells you about zero (the offset from point of aim). Read both together to diagnose yourself and your gun.; Also known as: grouping; See also: Zero / zeroing, Call the shot

H

HammerFirearm Parts: The hammer swings forward under spring pressure when the trigger is pressed, striking the firing pin which in turn strikes the primer. Modern striker-fired pistols use a striker instead.; See also: Striker-fired, Firing pin
Hammer spring (mainspring)Firearm Parts: The mainspring is usually a coil or leaf spring that powers the hammer. A weak mainspring causes light primer strikes and misfires. On revolvers the mainspring also affects trigger feel.; Also known as: mainspring; See also: Hammer, Light primer strike
Handload / reloadAmmunition: Handloading is the practice of assembling cartridges on a reloading press. It saves money, tailors accuracy, and provides access to cartridges that are scarce. It also requires training, attention, and meticulous process control: mistakes produce squibs, overpressure, or worse.; Also known as: reload, reloading, handloading; See also: Squib (squib load)
HangfireAmmunition: A hangfire is a perceptible delay (usually fractions of a second to a couple of seconds) between the primer strike and the powder burn. Rare with modern ammunition. If you suspect a hangfire, keep the muzzle pointed downrange for at least 30 seconds before opening the action.; See also: Squib (squib load), Light primer strike
HeadspaceAction Types: Headspace is measured with precision gauges and ensures the cartridge sits at exactly the right depth when the bolt is locked. Excessive headspace allows dangerous rearward gas leakage; insufficient headspace prevents the action from closing. This is gunsmith-level measurement.; Also known as: headspacing; See also: Chamber, Breech
Hearing protection (ear pro)Range and Gear: Gunfire is loud enough to cause permanent hearing damage from a single shot. Hearing protection is measured in NRR (Noise Reduction Rating). Electronic 'active' muffs amplify speech while blocking gunshots. Indoor ranges often warrant 'doubling up' (plugs under muffs).; Also known as: earpro, muffs, earplugs; See also: Eye protection (eye pro)
HeelingMarksmanship: Heeling is a form of recoil anticipation where the dominant palm pushes forward. Shots print high and sometimes strong-side. Fix with surprise-break trigger practice and conscious grip relaxation.; See also: Flinch
High readyMarksmanship: High ready is quicker in close quarters and reduces muzzle sweep of people below you. It is slower to present than low ready at arm's length but more protective in a crowd.; See also: Low ready, Sul position
HoldoffOptics and Sights: Holdoff is the horizontal equivalent of holdover. In a stiff crosswind you aim into the wind by a known number of mils or MOA to place the bullet on target. Faster than turret dialing under field conditions.; See also: Holdover
HoldoverOptics and Sights: Holdover uses reticle marks (or estimated offsets) to place shots at different ranges without touching the turrets. Faster than dialing, but demands a reticle calibrated to your ammunition. Common with BDC reticles or mil/moa grids.; See also: Bullet drop compensation (BDC), Holdoff
Hollow point (HP / JHP)Ammunition: Hollow-point bullets have a hollow cavity in the nose. On impact with soft tissue they expand (mushroom), creating a larger wound channel and dumping more energy in the target. They are the standard for self-defense because expansion reduces over-penetration. Jacketed Hollow Point (JHP) adds a copper jacket for reliable feeding.; Also known as: JHP, hollowpoint; See also: Full metal jacket (FMJ), ballistics
HolsterRange and Gear: A quality holster is firearm-specific, fully covers the trigger guard, retains the firearm through normal movement, and re-holsters without the help of the support hand. Materials include Kydex (rigid), leather, and hybrids. Fit the holster to the gun AND to your carry position (IWB, OWB, appendix).; See also: Concealed carry, Trigger discipline
HullAmmunition: The hull is the tube of a shotgun shell. Modern hulls are almost always plastic; paper hulls persist for classic side-by-side gunning. Hulls can be reloaded several times before the mouth frays too badly to crimp.; See also: Shotgun shell, Wad

I

IFAK (Individual First Aid Kit)Range and Gear: An IFAK is a focused bleeding-control kit carried at the range or in the vehicle. Minimum contents: CAT tourniquet, pressure dressing (Israeli/OLAES), hemostatic gauze (QuikClot/Celox), chest seal, gloves, trauma shears. Keep it reachable, not buried in a bag.; Also known as: IFAK, trauma kit; See also: Tourniquet
Illuminated reticleOptics and Sights: Illuminated reticles keep the aiming reference visible against dark targets or at dawn/dusk. LED illumination offers adjustable brightness but needs batteries; tritium glows continuously for years without power.; See also: Tritium, Reticle
Inertia-drivenAction Types: Inertia-driven actions rely on the shooter's body absorbing recoil while a spring-loaded bolt stays briefly stationary relative to the rearward-moving gun, then snaps back to cycle. Simpler and cleaner than gas-operated designs but pickier about light loads.; Also known as: recoil-operated; See also: Gas-operated
Inside the waistband (IWB)Legal and Carry: IWB carry rides between body and waistband, with a clip or loop attaching to the belt. It conceals better than OWB and adapts to many body types. Comfort depends heavily on the belt, holster fit, and pant sizing.; Also known as: IWB; See also: Outside the waistband (OWB), Appendix carry (AIWB)
Iron sightsOptics and Sights: Iron sights are the original sighting system: a front post or bead and a rear notch or peep. They are rugged, always-on, and require no batteries. Most new shooters start with iron sights, and they remain essential as a backup to electronic optics.; See also: Red dot (RDS), Sight picture
Isosceles stanceMarksmanship: Isosceles is named for the triangle formed by chest and extended arms. Body-armor-friendly, symmetric, and strong against recoil, it has largely supplanted the older bladed Weaver stance for defensive pistol work.; See also: Weaver stance, Stance

L

Light primer strikeAmmunition: A light primer strike is a shallow dent on the primer with no ignition. Common causes include fouling in the firing pin channel, weak mainspring, or excess oil damping pin travel. Cleaning and proper lubrication usually fix it.; Also known as: light strike; See also: Firing pin channel, Hammer spring (mainspring)
Loaded chamber indicator (LCI)Safety and Handling: LCIs range from a peek-through hole to a raised tab that protrudes when a round is in battery. They help under poor light or stress, but good training teaches a visual-and-tactile chamber check regardless of what the indicator says.; Also known as: LCI; See also: Four Rules of Firearm Safety
Low readyMarksmanship: Low ready keeps the muzzle safely downrange, lets you see the target and hands clearly, and supports a fast push-up to the sights. It's the default ready position for most defensive training.; See also: High ready, Sul position
Lower 1/3 co-witnessOptics and Sights: Lower-1/3 co-witness puts the red dot higher above the bore, so the irons only appear when you deliberately look for them. Favored on carbines for a cleaner primary sight picture with the iron sights available as backup.; See also: Co-witness, Absolute co-witness

M

M-LOKOptics and Sights: M-LOK (Modular Lock) is a Magpul-developed mounting standard that uses slots instead of a full rail profile. Lighter and slimmer than Picatinny, it has largely replaced KeyMod as the dominant accessory mount on modern carbines.; Also known as: mlok; See also: Picatinny rail
MagazineFirearm Parts: A magazine holds cartridges in a stack and feeds them one at a time as the action cycles. It is distinct from a clip (which is a loading device). Capacity limits vary by state law.; Also known as: mag; See also: Clip, Cartridge
Mantis X10 EliteRange and Gear: The Mantis X10 Elite is a motion-sensor training aid that mounts to a firearm and records micro-movements during each trigger press. It pairs with an app to diagnose flinch, anticipation, and grip issues. FST uses the X10 to give data-driven feedback during training.; See also: Dry fire, Trigger press
MilkingMarksmanship: Milking is the instinct for the whole hand to squeeze together on the trigger pull. The result is an irregular grip at the moment of ignition. Cured by isolated trigger-finger practice during dry fire.; See also: Trigger press, Grip
Milliradian (MIL / MRAD)Marksmanship: A milliradian (mil) is 1/1000 of a radian. Most modern tactical and military scopes use mils for both reticle subtensions and turret adjustments, which makes range estimation math cleaner in metric units.; Also known as: MRAD, mildot; See also: Minute of Angle (MOA), Zero / zeroing
Minute of Angle (MOA)Marksmanship: Minute of Angle is 1/60 of a degree. At 100 yards, 1 MOA is approximately 1.047 inches. Scope adjustments are often in fractions of MOA (e.g. 1/4 MOA per click), and rifle accuracy is often rated in MOA (a 'sub-MOA rifle' shoots groups smaller than 1 inch at 100 yards).; Also known as: minute of angle; See also: Milliradian (MIL / MRAD), Zero / zeroing
Muzzle disciplineSafety and Handling: Muzzle discipline is the habitual awareness of the direction your barrel is pointed at all times — loaded or unloaded, in your hand or holstered. It is the physical expression of Rules 1 and 2 of the four rules.; See also: Four Rules of Firearm Safety, Trigger discipline

N

NATO round (5.56 NATO / 7.62 NATO)Ammunition: NATO cartridges are standardized for interoperability among member nations. 5.56 NATO is dimensionally similar to .223 Remington but loaded to higher pressure (check your rifle's chamber marking). 7.62 NATO is dimensionally similar to .308 Winchester with similar pressure caveats.; Also known as: NATO, 5.56 NATO, 7.62 NATO; See also: Caliber, AR-15
Natural point of aim (NPA)Marksmanship: Natural point of aim is where the firearm settles when your muscles relax. If your NPA is off the target you'll fight it with every shot, costing accuracy and stamina. Finding NPA is a matter of shifting your whole body (not your arms) until the gun points at the target when relaxed.; Also known as: NPA; See also: Stance, Breath control
Negligent discharge (ND)Safety and Handling: A negligent discharge is any unintended firing of a firearm. The term 'negligent' (rather than 'accidental') reflects that nearly every ND traces back to a human violation of the four rules, most often trigger discipline or a failure to verify the gun was unloaded.; Also known as: ND, accidental discharge, AD; See also: Four Rules of Firearm Safety, Trigger discipline
NFA (National Firearms Act)Legal and Carry: The National Firearms Act imposes registration, a $200 tax stamp, and ATF approval for transfers of NFA items: short-barreled rifles (SBRs), short-barreled shotguns (SBSs), suppressors, machine guns, Any Other Weapons (AOWs), and destructive devices. Requirements apply at both purchase and interstate travel with NFA items.; Also known as: NFA; See also: SBR (Short-Barreled Rifle), Suppressor (silencer), ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives)
NICS background checkLegal and Carry: NICS is the federal background check system run by the FBI. Federally licensed firearm dealers (FFLs) must run a NICS check on buyers before a firearm transfer. Oregon adds a state requirement on top: a background check for private-party transfers too, not just dealer sales. Oregon does not have a mandatory waiting period.; Also known as: background check; See also: Federal Firearms License (FFL)
NIJ ratingRange and Gear: NIJ ratings certify body armor against specific threat levels. IIA-IIIA are soft panels rated for handgun rounds. Level III stops common rifle rounds (7.62x51 FMJ); Level IV stops armor-piercing rifle rounds. Always match armor to realistic threats and understand its limits.; Also known as: NIJ; See also: soft-armor
NRA (National Rifle Association)Legal and Carry: The NRA is the oldest civil-rights organization in the United States. Its training division certifies instructors and publishes well-known beginner curricula. Some communities prefer alternative training organizations; FST offers LGBTQIA+-focused instruction that is independent of the NRA.; Also known as: NRA

O

OgiveAmmunition: The ogive is the tapered section between the bullet's shoulder and tip. Sharp ogives slip through the air better at range; blunt ogives feed more reliably in certain actions. Competition shooters measure overall length to a specific ogive point for consistency.; See also: Bullet, Boat tail
Open carryLegal and Carry: Open carry is the practice of carrying a visible firearm in public. It is legal in much of the United States, but many cities and private properties restrict or prohibit it. In Oregon, open carry is generally legal but some cities (like Portland) have additional restrictions in public buildings and parks.; See also: Concealed Handgun License (CHL), Concealed carry
Outside the waistband (OWB)Legal and Carry: OWB carry is standard for duty, range, and open carry. It is typically more comfortable than IWB for extended periods but requires longer cover garments to conceal. Better access for shooters with mobility constraints.; Also known as: OWB; See also: Inside the waistband (IWB), Open carry
Over-grippingMarksmanship: A too-hard grip produces shake and makes the trigger press ragged. Aim for consistent, repeatable pressure rather than maximum force. Many instructors call this the '7/10 rule' — firm enough to control recoil, relaxed enough to hold steady.; Also known as: death grip; See also: Grip

P

+PAmmunition: +P rounds are loaded to higher SAAMI-approved pressures for more velocity and energy, at the cost of increased recoil and accelerated wear. Always verify the firearm is +P-rated before routine use; many older designs are not.; Also known as: plus-p; See also: +P+
+P+Ammunition: +P+ is an informal designation for loads beyond SAAMI +P pressures, typically produced for law enforcement or specific platforms. Without an industry-wide standard, only use +P+ in firearms explicitly approved for it.; Also known as: plus-p-plus; See also: +P
ParallaxOptics and Sights: Parallax happens when the reticle and target images are not at the same optical plane. You notice it when the reticle seems to drift across the target as you move your head. Many scopes have a parallax adjustment (often a side knob) to remove it at a given distance.; See also: Scope (rifle scope), First focal plane (FFP), Second focal plane (SFP)
Pattern (shot pattern)Ammunition: Patterning your shotgun means firing a given load at 30 or 40 yards and measuring how many pellets fall inside a 30-inch circle. Every barrel, choke, and load combination produces a different pattern. Patterning is mandatory before relying on a shotgun for defense or hunting.; See also: Choke, Shotgun shell
Penny drillMarksmanship: The penny drill is a self-diagnostic for trigger control. Balance a coin on the front sight (or the slide), press through in dry fire, and see whether the coin survives. It's cheap, silent, and humbling.; See also: Trigger jerk, Dry fire
Picatinny railOptics and Sights: Picatinny rails are the universal mounting interface on most modern firearms. The numbered cross-slots let optics clamp securely and return to the same position after removal. Don't confuse with the similar-looking Weaver rail (different slot spacing).; Also known as: pic rail; See also: M-LOK
Prep the triggerMarksmanship: Prepping the trigger means applying partial pressure to remove pre-travel while the sights are still settling. When the sights are right, a minimal additional press breaks the shot cleanly. Used in precision and competition shooting; not a beginner habit.; See also: Trigger staging, Trigger press
PresentationMarksmanship: A clean presentation grips the gun in the holster, clears, rotates to the target, joins hands, and extends out to full sight picture in one continuous motion. Consistency beats speed; smooth becomes fast with repetition.; See also: Draw stroke, Sight picture
PrimerAmmunition: The primer is a small metal cup filled with shock-sensitive compound, seated into the base of a cartridge case. The firing pin strikes it, it ignites the powder, and the powder's rapid burn launches the bullet. Primers are either 'boxer' or 'berdan' style; boxer is standard in the US.; See also: Firing pin, Cartridge
PrintingLegal and Carry: Printing happens when a garment is too tight or thin, or when you move in ways that pull cloth against the gun. It reveals you're armed to anyone looking. Proper garment cut, holster geometry, and movement awareness prevent it.; See also: Concealed carry, Appendix carry (AIWB)
Pump-actionAction Types: Pump-action is the dominant shotgun action type. The shooter pulls the forend rearward to eject the spent shell, then pushes it forward to chamber the next. Pump guns are extremely reliable because the shooter provides all cycling energy.; Also known as: slide-action; See also: Break-action, Semi-automatic

R

Ready positionMarksmanship: Ready positions balance safety, awareness, and speed to first shot. Choice depends on distance, environment, and the number of targets. Training should include transitions from each ready position to the target.; See also: Low ready, High ready, Sul position
ReceiverFirearm Parts: The receiver is the long-gun equivalent of a pistol frame: the central metal body that holds the bolt, trigger group, and other working parts. On AR-pattern rifles it is split into an upper (barrel/bolt) and lower (trigger/stock) receiver.; See also: Frame, Bolt-action
RecoilMarksmanship: Recoil is the rearward momentum the shooter feels when a round fires — Newton's third law at work. Felt recoil depends on cartridge power, firearm weight, action type, and shooter technique. Proper grip and stance manage recoil and keep follow-up shots fast.; Also known as: kick; See also: Stance, Grip
Recoil springFirearm Parts: The recoil spring stores energy when the slide cycles rearward and returns the slide forward to chamber the next round. A tired recoil spring causes short-stroking and feeding failures. Replacement every 3,000 to 5,000 rounds is a common interval.; Also known as: return spring; See also: Slide, Bolt carrier group (BCG)
Red dot (RDS)Optics and Sights: A red dot sight projects an LED dot onto a lens in the shooter's line of sight. You focus on the target, place the dot, and press. It removes the need to align front and rear sights, is fast, and works well with both eyes open. Common on pistols, rifles, and shotguns.; Also known as: RDS, reflex sight; See also: Iron sights, Minute of Angle (MOA), Zero / zeroing
Red flag law (ERPO)Legal and Carry: Red flag laws (Extreme Risk Protection Orders) are civil procedures where family members, household members, or law enforcement can petition a court to temporarily suspend someone's firearm rights. Oregon has an ERPO statute (ORS 166.525-166.543). Subject to due-process requirements including a hearing.; Also known as: ERPO, Extreme Risk Protection Order
Retention levelLegal and Carry: Retention levels count active locks beyond passive friction. Level I is friction only, Level II adds one active lock, Level III adds a second, and so on. Higher retention defeats weapon grabs better but slows down the draw.; See also: Duty holster
ReticleOptics and Sights: The reticle is the aiming reference visible through a scope or red dot. Designs range from simple crosshairs to Christmas-tree reticles with wind and drop holds. Reticle choice should match the shooter's intended distance and lighting.; Also known as: crosshair, crosshairs; See also: Scope (rifle scope), Bullet drop compensation (BDC)
RevolverAction Types: A revolver stores rounds in a rotating cylinder rather than a magazine. Pressing the trigger (double-action) or cocking the hammer (single-action) indexes the cylinder to line up the next chamber with the barrel. Revolvers are mechanically simple and very reliable.; See also: Chamber, Double-action (DA / DAO / DA/SA)
Rifled slugAmmunition: Rifled slugs (also called Foster slugs) have angled grooves on the outside. The grooves do not spin the slug; they let it safely pass through shotgun chokes. Rifled slugs stabilize aerodynamically and are designed for smoothbore shotgun barrels.; See also: Slug, Sabot slug, Smoothbore
RimfireAmmunition: In a rimfire cartridge the priming compound is spun into the folded rim of the case. The firing pin crushes the rim against the chamber edge to ignite. Rimfire is cheap and low-recoil, making it ideal for training, but low-powered and not reloadable.; See also: Centerfire, Primer

S

Sabot slugAmmunition: Sabot slugs use a plastic sleeve to engage the rifling in a dedicated slug barrel. The sleeve separates downrange, leaving the slug spinning for stability. Effective range can exceed 150 yards. Requires a rifled shotgun barrel, not a smoothbore.; See also: Slug, Rifled slug
Safety (mechanical)Firearm Parts: A mechanical safety physically blocks some part of the firing chain when engaged. Types include manual thumb safeties, grip safeties, trigger safeties, and drop safeties. Mechanical safeties can fail and are never a replacement for the four rules of firearm safety.; See also: Four Rules of Firearm Safety
SBR (Short-Barreled Rifle)Legal and Carry: Federal law defines an SBR as a rifle with a barrel shorter than 16 inches or total length shorter than 26 inches. Ownership requires NFA registration, a $200 tax stamp, and ATF approval. Crossing state lines with an SBR requires prior ATF notification via Form 5320.20.; Also known as: SBR; See also: NFA (National Firearms Act), ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives)
SBS (Short-Barreled Shotgun)Legal and Carry: SBSs carry the same NFA registration, tax stamp, and approval requirements as SBRs. Barrel length and overall length are both measured; either under the limit triggers NFA regulation.; Also known as: SBS; See also: NFA (National Firearms Act), SBR (Short-Barreled Rifle)
Scope (rifle scope)Optics and Sights: A rifle scope uses lenses to magnify the target and provides a reticle for aiming. Modern scopes offer variable magnification, illuminated reticles, and precise turret adjustments. Selection depends on the rifle's role (hunting, precision, close-range).; See also: Minute of Angle (MOA), Milliradian (MIL / MRAD), Zero / zeroing
Second focal plane (SFP)Optics and Sights: SFP scopes keep the reticle visually constant while the image around it zooms. Simpler and cheaper than FFP, but holdover marks are calibrated for a specific magnification (usually max). Most hunting scopes are SFP.; Also known as: second focal plane, rear focal plane; See also: First focal plane (FFP)
Semi-automaticAction Types: A semi-automatic firearm uses energy from firing (recoil or tapped gas) to eject the spent case and chamber a new round. One press of the trigger fires one shot. This is the dominant modern design for pistols and many rifles.; Also known as: semi-auto, autoloader; See also: Slide, Bolt-action
Short-strokingAction Types: Short-stroking is a shooter error on pump guns: the forend is not pulled far enough back or pushed far enough forward. The fix is simple but counterintuitive under stress: cycle the action with authority, all the way back and all the way forward.; See also: Pump-action
Shotgun shellAmmunition: Shotgun shells use a plastic hull with a brass base. Birdshot and buckshot loads contain many pellets; slug loads contain a single projectile. The shell is usually crimped at the end, and fires from a smoothbore barrel (with exceptions for rifled slug barrels).; Also known as: shell, shotshell; See also: Gauge, Buckshot, Birdshot, Slug
Show clearSafety and Handling: Showing clear means removing any source of ammunition (magazine), cycling or locking the action open, and presenting the chamber for visual verification. It is the standard way to prove a firearm is safe before handing it off, storing it, or stepping away from the line.; See also: Cease-fire, Four Rules of Firearm Safety
Sight alignmentMarksmanship: Sight alignment refers only to the relationship of the front and rear sights to each other: front centered in the rear notch, equal light gaps on either side of the front post, and tops level. Sight picture adds the target to this equation.; See also: Sight picture
Sight pictureMarksmanship: Sight picture is the complete view through your sights when everything is aligned: front sight focused and level with the rear, centered in the notch, held on the desired point on the target. For most handgun shooting the front sight is in sharp focus while the target is slightly blurry.; See also: Sight alignment, Trigger press
Single-action (SA / SAO)Action Types: A single-action trigger performs one job: releasing an already-cocked hammer or striker. The pull is typically short and light. 1911-pattern pistols are classic examples; they must be carried cocked-and-locked or manually cocked before the first shot.; Also known as: SA, SAO, single action only; See also: Double-action (DA / DAO / DA/SA), Striker-fired
SlideFirearm Parts: On a semi-automatic pistol, the slide cycles rearward under recoil, ejects the spent case, and strips a new cartridge from the magazine on its return. It houses the barrel, extractor, and firing pin or striker.; See also: Semi-automatic, Striker-fired, Recoil
Slide railsFirearm Parts: Slide rails are precision-machined tracks on the frame. Good lubrication here is critical to reliable cycling. Dry or gritty rails cause sluggish slide action and malfunctions.; Also known as: rails; See also: Slide, Frame
SlugAmmunition: Shotgun slugs are single solid projectiles, typically 7/8 to 1-1/4 ounces. They hit far harder than any pistol round but require more aim than buckshot. Rifled slugs work in smoothbore barrels; sabot slugs work in rifled shotgun barrels.; See also: Rifled slug, Sabot slug, Smoothbore
SmoothboreAmmunition: Most shotgun barrels are smoothbore: the bore is a smooth tube with no spiral grooves. Pellets and rifled slugs work here. Sabot slugs require a rifled barrel. Smoothbores are cheaper, simpler, and easier to clean than rifled barrels.; See also: Rifled slug, Sabot slug
Snap capMarksmanship: Snap caps let you cycle, dry-fire, and practice malfunction drills without using live rounds and without dry-firing on an empty chamber (which can stress firing pins in rimfire and some older designs).; Also known as: dummy round; See also: Dry fire, Ball-and-dummy drill
Soft point (SP)Ammunition: Soft points have a jacketed body with lead exposed at the tip. On impact the lead mushrooms and expands the projectile. They are a hunting mainstay and feed more reliably than some hollow-point designs in older actions.; See also: Hollow point (HP / JHP), Full metal jacket (FMJ)
Squib (squib load)Ammunition: A squib is usually signaled by a muffled 'pop,' negligible recoil, and no bullet impact downrange. Firing another round behind a lodged bullet WILL rupture the barrel. If you suspect a squib, stop, unload, and check the bore with a cleaning rod before firing again.; See also: Hangfire, Light primer strike
StanceMarksmanship: A good shooting stance is athletic and stable: feet shoulder-width, slight forward lean, weight balanced toward the balls of the feet. Isosceles (square to target) is the modern standard; Weaver (bladed) is an older alternative. Stance manages recoil and supports consistent follow-up shots.; See also: Grip, Recoil
Stand your groundLegal and Carry: Stand-your-ground laws extend castle doctrine concepts to places outside the home where the person is lawfully present. Oregon is NOT a stand-your-ground state. Oregon's use-of-force standard requires that force be 'necessary' and proportional; consult a lawyer for specifics.; See also: Castle doctrine, Duty to retreat
Straw purchaseLegal and Carry: A straw purchase is when a qualified buyer purchases a firearm for an unqualified buyer or to hide the true owner. Lying on ATF Form 4473 about this is a federal felony (up to 10 years). Gift purchases between legal buyers are NOT straw purchases as long as the giver is the true purchaser.; See also: Federal Firearms License (FFL), NICS background check
Striker-firedAction Types: Striker-fired pistols use a partially pre-tensioned internal striker rather than an external hammer. The trigger pull finishes cocking and then releases the striker. Designs are typically simple, with consistent trigger pulls and no manual de-cocking.; See also: Hammer, Single-action (SA / SAO), Double-action (DA / DAO / DA/SA)
SubsonicAmmunition: Subsonic loads use heavier bullets and reduced powder to keep the bullet below supersonic speed, eliminating the sonic crack. Combined with a suppressor, subsonic fire is genuinely quiet. Trade-off is reduced energy and range.; See also: Supersonic
Sul positionMarksmanship: Sul (Portuguese for 'south') is a close-quarters carry position where the muzzle points at the ground along the body's centerline. It keeps the muzzle off bystanders and teammates while allowing fast presentation.; Also known as: sul; See also: Low ready, High ready
SupersonicAmmunition: Most factory ammunition is supersonic. The bullet breaks the sound barrier on the way downrange and produces a crack that is audible regardless of suppressor use. Supersonic loads deliver full-power energy and range.; See also: Subsonic
Support handMarksmanship: The support hand should do most of the gripping work, freeing the trigger hand to operate the trigger smoothly. Modern technique places the support thumb forward and the palm high on the grip for maximum recoil control.; Also known as: weak hand; See also: Grip
Suppressor (silencer)Range and Gear: Suppressors don't make firearms movie-quiet — they reduce peak noise from around 160 dB to 130-140 dB, comparable to a jackhammer. They help preserve hearing and reduce recoil and muzzle flash. Federally regulated under the NFA: $200 tax stamp, ATF approval, registered ownership.; Also known as: silencer; See also: NFA (National Firearms Act), Subsonic
Surprise breakMarksmanship: A surprise break is the goal of pure trigger control: you apply steady pressure while holding the sight picture, and the shot 'just happens.' If you can predict the exact instant the gun will fire you will flinch. Dry-fire practice trains this.; See also: Flinch, Trigger press

T

Takedown pinFirearm Parts: Takedown pins are cylindrical pins (one or two, depending on design) that let you separate major assemblies for cleaning. On AR-15s the takedown and pivot pins separate upper and lower receivers; on many pistols a single takedown lever releases the slide.; Also known as: pivot pin; See also: field-strip
Target acquisitionMarksmanship: Target acquisition is the chain from 'see' to 'sights on target.' Training speeds this process through drilling the draw, transitions, and sight pick-up. Before firing, acquisition must include target identification and what lies behind it.; See also: Presentation, Transition
ThumbingMarksmanship: Thumbing comes from tight dominant-thumb pressure. Typical cure: adopt a high thumbs-forward grip with both thumbs off the frame, pointed toward the target.; See also: Grip
TourniquetRange and Gear: A tourniquet is the first-line treatment for massive limb bleeding from firearm injuries. Apply 2-3 inches above the wound, tighten until bleeding stops, note the time. Only CAT (Combat Application Tourniquet) and SOFTT-W are considered field-proven. Improvised tourniquets are a last resort.; See also: IFAK (Individual First Aid Kit)
TransitionMarksmanship: Transitioning between targets efficiently means snapping your eyes to the next target first, then driving the gun to follow your vision. Good transitions control the recoil of the previous shot so the gun arrives ready to fire again.; See also: Controlled pair, Target acquisition
TriggerFirearm Parts: The trigger is the lever that releases the hammer or striker to fire the cartridge. Trigger 'pull weight' (force required) and 'travel' (distance) are key feel characteristics and vary across single-action, double-action, and striker-fired designs.; See also: Single-action (SA / SAO), Double-action (DA / DAO / DA/SA), Striker-fired, Trigger discipline
Trigger disciplineSafety and Handling: Trigger discipline means the finger stays indexed along the frame (outside the trigger guard) except at the moment of firing. It is the physical expression of Rule 3 of the four rules and prevents the vast majority of negligent discharges.; See also: Four Rules of Firearm Safety, Negligent discharge (ND)
Trigger jerkMarksmanship: Trigger jerk is a discrete, fast pull. It disturbs sight alignment before the shot breaks. Dry fire with a coin balanced on the front sight is a classic diagnostic: the coin falls if you jerk.; See also: Trigger press, Penny drill
Trigger pressMarksmanship: A controlled, straight-to-the-rear trigger press is the foundation of accuracy. Most new-shooter misses come not from aim but from jerking or anticipating. Dry-fire practice builds this skill more efficiently than live fire.; Also known as: trigger pull, trigger squeeze; See also: Sight picture, Dry fire
Trigger resetMarksmanship: Most modern pistols have a short reset: you let the trigger travel forward just enough to hear/feel a click, then press again. Riding the reset produces faster, more consistent follow-up shots than fully releasing the trigger.; Also known as: reset; See also: Trigger press, Controlled pair
Trigger stagingMarksmanship: Staging is most useful on long, heavy double-action pulls. The shooter walks the trigger to the break, holds while finalizing the sight picture, and then breaks with minimal additional motion. Not typically used with striker-fired pistols.; See also: Double-action (DA / DAO / DA/SA), Prep the trigger
TritiumOptics and Sights: Tritium is a hydrogen isotope that emits light as it decays (half-life ~12 years). Encapsulated in small vials it lights up iron sights and some reticles without batteries. The dose is tiny and shielded by the sight body.; See also: Illuminated reticle, Iron sights

U

USCCA (U.S. Concealed Carry Association)Legal and Carry: The USCCA provides concealed-carry training materials and a membership that includes self-defense legal protection coverage (attorney fees and civil liability). A common pick for people who carry concealed; alternatives include Second Call Defense and CCW Safe.; Also known as: USCCA; See also: Concealed carry, Concealed Handgun License (CHL)

W

WadAmmunition: The wad cups the pellets together inside the hull and seals against the barrel as the shot accelerates. Once clear of the muzzle it falls away from the shot column. Wads are often recovered downrange.; See also: Shotgun shell, Hull
WadcutterAmmunition: Wadcutters have a flat or slightly concave nose that cuts crisp holes in paper, which helps scoring in bullseye competition. Not suited for semi-auto feeding or defensive use, but excellent for revolvers at the target range.; See also: Full metal jacket (FMJ)
Weaver stanceMarksmanship: Weaver places the support-side foot forward, angles the body to the target, and creates push-pull tension with a bent trigger arm and straight support arm. Still taught historically, but isosceles dominates modern defensive pistol training.; See also: Isosceles stance, Stance
Windage turretOptics and Sights: The windage turret moves the reticle left and right. Windage adjustments are most commonly used for cross-winds at range. Like elevation, calibrated in MOA or mil clicks.; See also: Elevation turret

Z

Zero / zeroingMarksmanship: To zero a firearm is to adjust its sights or scope so that where you aim is where it hits at a given distance. Common handgun zeros are 25 yards; rifle zeros vary by purpose (50-yard, 100-yard, or 36-yard 'battle zero' for 5.56mm).; Also known as: zeroing, sight-in; See also: Minute of Angle (MOA), Sight picture

Question about a term?

Glossaries are easier to remember with a real firearm in your hands. Come shoot with us.

Book a Familiarization

Firearms Glossary

By Category

Safety and Handling

Firearm Parts

Action Types

Ammunition

Marksmanship

Optics and Sights

Legal and Carry

Range and Gear

A to Z

A

B

C

D

E

F

G

H

I

L

M

N

O

P

R

S

T

U

W

Z

Question about a term?

Firearms Glossary

By Category

Safety and Handling

Firearm Parts

Action Types

Ammunition

Marksmanship

Optics and Sights

Legal and Carry

Range and Gear

A to Z

A

B

C

D

E

F

G

H

I

L

M

N

O

P

R

S

T

U

W

Z

Question about a term?