A

ACP — Automatic Colt Pistol. Commonly used in cartridge names such as .45 ACP.

Action — The working mechanism of a firearm that loads, fires, extracts, and ejects ammunition.

Accidental Discharge — A firearm discharge caused by a true mechanical failure or circumstance outside the shooter’s control. These are rare. Most unintended shots are better described as negligent discharges.

Ammunition — The complete components needed to fire a gun: case, primer, powder, and projectile. A single unit is usually called a cartridge or round.

Antique Firearm — Generally, a firearm manufactured before 1899 or one that uses ammunition not commonly available.

Assault Rifle — A military firearm capable of selective fire, meaning it can fire in semi-automatic and fully automatic modes.

Assault Weapon — A political and legal term that changes depending on the jurisdiction. It is not the same thing as an assault rifle.

Automatic Firearm — A firearm that continues firing as long as the trigger is held and ammunition remains available.

B

Backstop — A safe barrier that stops bullets after they pass through or miss the target.

Ballistics — The study of what happens when a projectile is fired. Internal ballistics happens inside the gun, external ballistics happens in flight, and terminal ballistics happens when the projectile strikes something.

Barrel — The metal tube the bullet travels through when fired.

Battery — A firearm is “in battery” when the action is fully closed and ready to fire. A firearm “out of battery” may be unsafe or unable to fire.

Berm — A mound of earth used as a backstop on an outdoor shooting range.

Birdshot — Shotgun ammunition loaded with small pellets, commonly used for hunting birds and clay target shooting.

Blowback — A firearm operating system where rearward pressure from firing moves the slide or bolt without a locked breech.

Bore — The inside of the barrel.

Brass — Common slang for spent cartridge cases.

Breech — The rear portion of the barrel where the cartridge is loaded.

Buckshot — Shotgun ammunition loaded with larger pellets, often used for defense or hunting.

Bullet — The projectile that leaves the barrel. The bullet is only one part of a cartridge.

C

Caliber — The diameter of a bullet or bore, often measured in inches or millimeters.

Carbine — A shorter rifle, often easier to maneuver than a full-length rifle.

Cartridge — A complete round of ammunition containing the case, primer, powder, and bullet.

Case / Casing — The container that holds the primer, powder, and bullet together.

Centerfire — Ammunition with the primer located in the center of the cartridge base.

Chamber — The part of the barrel or cylinder that holds the cartridge before it is fired.

Choke — A constriction at the muzzle end of a shotgun barrel that affects the spread of shot.

Clearing — The process of unloading a firearm and verifying that it is empty.

Clip — A device used to hold cartridges together for loading. A clip is not the same thing as a magazine.

Cold Range — A range condition where firearms are unloaded unless the shooter is actively on the firing line under instruction.

Compensator — A device attached to the muzzle that redirects gas to help reduce muzzle rise.

Concealed — Hidden from ordinary view. A concealed handgun is carried so it is not openly visible.

Controlled Pair — Two aimed shots fired quickly, with the shooter regaining the sights for the second shot.

Cover — Something that can stop or greatly slow bullets.

Cover Garment — Clothing used to conceal a handgun carried on the body.

D

Decocker — A lever that safely lowers the hammer on certain double-action firearms without firing the gun.

Double Action — A trigger system where pulling the trigger both cocks and releases the hammer or striker.

Double Action / Single Action — A firearm that fires the first shot in double action and later shots in single action.

Double Feed — A malfunction where the firearm tries to feed a new round while another casing or round is still blocking the chamber.

Double Tap — Two shots fired quickly. Often confused with a controlled pair.

Downrange — The area forward of the firing line where bullets are intended to travel.

Drop Safety — A mechanical safety designed to prevent the gun from firing if dropped.

Dry Fire — Practicing trigger press and gun handling without live ammunition. Dry fire must only be done with a verified unloaded firearm in a safe direction.

Dummy Round — An inert training round used for practice, loading drills, or malfunction training.

E

Ear Protection — Plugs or muffs used to protect hearing while shooting.

Ejector — The part that helps throw the spent case out of the firearm.

Ejection Port — The opening where spent cases exit a semi-automatic firearm.

Extractor — The part that pulls the case from the chamber.

External Safety — A safety lever or switch located on the outside of the firearm.

Eye Protection — Safety glasses worn to protect the eyes from brass, debris, fragments, and other hazards.

F

Factory Ammunition — Ammunition manufactured commercially, as opposed to handloads or reloads.

Failure to Feed — A malfunction where the firearm does not properly feed a new round into the chamber.

Failure to Fire — A malfunction where the gun does not fire when the trigger is pressed.

Firearm — A gun that uses gunpowder as a propellant. Airguns are not firearms under the common federal definition.

Firing Line — The line from which shooters fire downrange.

Firing Pin — The part that strikes the primer to ignite the cartridge.

Flinch — An involuntary movement before the shot, often caused by recoil anticipation.

Follow Through — Maintaining control of the trigger, sights, and grip after the shot breaks.

Four Rules of Firearm Safety — The basic safety rules that apply every time a firearm is handled:

• Treat all guns as if they are loaded.
• Never point the muzzle at anything you are not willing to destroy.
• Keep your finger off the trigger until your sights are on target and you have made the decision to fire.
• Be sure of your target and what is beyond it.

Front Sight — The sight located nearest the muzzle.

Full Metal Jacket — A bullet with a lead core covered by a harder metal jacket.

G

Gas Operated — A firearm system that uses gas pressure from the fired cartridge to cycle the action.

Gauge — The common measurement used for shotgun bore size.

Grip — The part of a handgun held by the shooter, or the way the shooter holds the firearm.

Grip Safety — A safety located on the grip that must be depressed before the gun can fire.

Group — A cluster of bullet holes on a target.

Gunpowder — The propellant that burns to create pressure and drive the projectile.

H

Hammer — The part that strikes the firing pin or primer on some firearms.

Handgun — A firearm designed to be fired with one or both hands rather than from the shoulder.

Handloads — Ammunition assembled by an individual rather than a commercial manufacturer.

Heavy Trigger — A trigger that requires more pressure to fire.

Hollow Point — A bullet designed with a cavity in the nose, often intended to expand after impact.

Holster — A device used to safely carry a handgun. A proper holster should cover the trigger guard, retain the gun, and allow safe access.

Hot Range — A range condition where firearms may be loaded under range rules or instructor direction.

I

Integral Lock — A built-in locking device that may prevent the firearm from firing.

Internal Safety — A safety mechanism inside the firearm, often designed to prevent firing if dropped.

Iron Sights — Traditional mechanical sights, usually a front sight and rear sight.

Isosceles Stance — A shooting stance where the arms extend forward in a triangle-like shape.

J

Jacket — The metal covering around the core of a bullet.

Jam — A serious malfunction that may require tools or extra effort to clear. Many simple stoppages are incorrectly called jams.

K

Keyhole — An oddly shaped bullet hole caused when a bullet strikes sideways instead of nose-first.

Kick — Slang for recoil.

L

Lands — The raised portions inside a rifled barrel between the grooves.

Laser — An aiming device that projects a visible dot onto the target area.

Length of Pull — The distance from the trigger to the rear of the stock, or the distance a trigger travels depending on context.

Lever Action — A firearm action operated by moving a lever down and back up.

Limp Wristing — Poor wrist support while shooting a semi-automatic handgun, which can contribute to malfunctions.

Loaded — A firearm is loaded when ammunition is in the chamber, cylinder, or magazine depending on context. For safety, all guns should be treated as loaded.

Loaded Chamber Indicator — A device that gives visual or tactile notice that a round is in the chamber.

Long Gun — A firearm designed to be fired from the shoulder, such as a rifle or shotgun.

M

Machine Gun — A fully automatic firearm that fires more than one round with a single pull of the trigger.

Magazine — A device that stores cartridges under spring pressure and feeds them into the firearm.

Magazine Disconnect — A device that prevents the gun from firing when the magazine is removed.

Magazine Loader — A tool used to help load cartridges into a magazine.

Magazine Well — The opening where a detachable magazine is inserted.

Magnum — A term usually describing a more powerful cartridge or load.

Malfunction — A stoppage or failure that prevents the firearm from operating properly.

Manual Safety — A safety device that must be manually engaged or disengaged by the shooter.

Misfire — A cartridge failure where the round does not fire when struck.

Moon Clip — A metal device used to hold rimless cartridges together for use in some revolvers.

Muzzle — The front end of the barrel where the projectile exits.

Muzzle Control — Keeping the firearm pointed in a safe direction at all times.

Muzzle Brake — A device that redirects gas to reduce recoil.

N

Negligent Discharge — An unintended shot caused by a failure to follow safety rules. This is different from a true mechanical accident.

NFA — The National Firearms Act, which regulates items such as machine guns, short-barreled rifles, short-barreled shotguns, and suppressors.

Night Sights — Sights designed to be visible in low light, often using tritium or glow material.

O

Off Hand — Can mean shooting while standing unsupported, or the shooter’s non-dominant hand.

Open Sights — A sight system with a rear notch and front sight blade.

Out of Battery — A condition where the action is not fully closed. A firearm out of battery may not be safe to fire.

Over / Under — A shotgun with two barrels stacked vertically.

P

+P Ammunition — Ammunition loaded to higher pressure than standard. Not all firearms are designed for +P ammunition.

Passive Safety — A safety that works without the shooter manually switching it on or off.

Pattern — The spread of shotgun pellets on a target.

Pistol — A handgun. The term is often used for semi-automatic handguns, but it can also broadly include handguns.

Point Shooting — Shooting without using the sights. This is often discussed in defensive shooting but should not replace sighted fire training.

Porting — Openings near the muzzle that redirect gas to reduce muzzle rise, often increasing noise and flash.

Primer — The small ignition component in the cartridge that starts the firing process.

Printing — When the outline of a concealed handgun can be seen through clothing.

Propellant — The powder that burns and produces gas pressure to move the projectile.

Pump Action — A firearm action operated by moving the fore-end back and forward.

R

Racking the Slide — Pulling the slide fully to the rear and releasing it to chamber a round or clear the firearm.

Rail — A mounting surface for accessories such as lights or lasers.

Range — A designated place for firearm practice or qualification.

Rear Sight — The sight located closest to the shooter.

Recoil — The rearward movement of a firearm after firing.

Red Dot Sight — An optical sight that uses a projected dot as an aiming reference.

Reload — To replenish ammunition in the firearm.

Revolver — A handgun with a rotating cylinder that holds cartridges.

Rifling — Spiral grooves inside a barrel that spin the bullet for stability.

Rimfire — Ammunition with primer compound around the rim of the case, such as .22 LR.

Round — One complete cartridge of ammunition.

S

Safe Direction — A direction where an unintended shot would be least likely to cause injury or serious damage. “Down” is not automatically safe in every environment.

Safety — A mechanical device or handling procedure intended to reduce the chance of an unintended discharge.

Semi-Automatic — A firearm that fires one round per trigger press and uses the energy of firing to cycle the next round.

Shell — Common term for shotgun ammunition, and sometimes used for cartridge cases.

Sight Alignment — The relationship between the front and rear sights.

Sight Picture — Sight alignment placed on the target.

Single Action — A trigger system where the trigger releases a cocked hammer or striker but does not cock it.

Slide — The upper moving portion of many semi-automatic pistols.

Snap Cap — A dummy round designed for dry fire or practice.

Squib Load — A dangerous ammunition malfunction where the bullet may lodge in the barrel. Stop shooting immediately if a squib is suspected.

Stance — The shooter’s body position while firing.

Striker-Fired — A firing system using a spring-loaded striker rather than a traditional hammer.

Suppressor — A regulated device attached to the firearm to reduce the sound signature. It does not make a firearm silent.

T

Tap, Rack — A common immediate-action method for clearing certain semi-automatic handgun stoppages.

Target — The intended object or area being shot.

Terminal Ballistics — The study of what a projectile does after impact.

Thumb Safety — A manual safety usually operated by the firing-hand thumb.

Trigger — The part pressed by the shooter to fire the gun.

Trigger Break — The point where trigger pressure releases the hammer or striker.

Trigger Control — Pressing the trigger without disturbing the sights or muzzle.

Trigger Guard — The loop surrounding the trigger.

W

Weaver Stance — A shooting stance using a bladed body position and push-pull tension.

Wheel Gun — Slang for revolver.

Windage — Horizontal sight adjustment.

Wound Channel — The path of tissue disruption caused by a projectile.