Definition. The act of defining or making definite, distinct or clear. The formal statement of the meaning or significance of a word or phrase. If you are new to shooting there may be words used that you are not really sure of the meaning. Maybe you thought ACP stood for Automatic Cartridge Pistol and not Automatic Colt Pistol? If you are unsure of a meaning check out the definitions we’ve collected below. Want to see a term added to this page? Post a comment and we will research and get a definite answer for you. Let’s take a shot at explaining some common firearm terms.
ACP - Automatic Colt Pistol. Colt's proprietary designation for a type of rimless cartridge design, such as .45 ACP.
Action - The part of a firearm (the receiver) that loads fires, and ejects a cartridge. There are several types of action including lever action, pump action, bolt action, and semi-automatic.
Ammunition - One or more loaded cartridges consisting of a primed case, propellant, and projectile. Three main types are rimfire, centerfire, and shotshell.
Automatic - A firearm that will fire continuously as long a the trigger is held back until the magazine is empty. An example would be a machine gun. A firearm activated as above, but which shoots only one bullet with each separate pull of the trigger, while often erroneously referred to as "automatic" is more properly termed Semi-Automatic.
Ballistics - The study of a projectile in motion. Backstrap - Rear, metal, part of a handgun---which together with the frontstrap, provides a mounting frame for the grips.
Barrel - The metal tube through which a projectile or shot charge is fired. May be rifled or smooth.
Barrel Length - The length of a barrel as measured from the muzzle to the standing breech in a break-open gun or to the bolt face in a bolt-action rifle, including the chamber. A revolver barrel measurement does not include the cylinder, only the barrel itself.
Blue/Bluing - A chemical rust process that produces a very dark, almost black, blue finish to the steel parts of a firearm which enhances the appearance and provides some protection from unwanted rust. Sometimes it can have a slight brownish undertone.
Bolt - The locking and cartridge head supporting mechanism of some firearm designs that contains the firing pin, extractor, and sometimes the ejector. Most frequently bolt action is used on rifles.
Bore - The inside of the barrel. "Smoothbore" weapons (typically shotguns) have no rifling. Most handguns and rifles have "rifling".
Brass - Used for fired cartridge cases.
Bullet - The projectile. They are shaped or composed differently for a variety of purposes. round-nose - The end of the bullet is blunted. Hollow-point - There is a hole in the bullet that creates expansion when a target is struck, creating more damage. Jacketed - The soft lead is surrounded by another metal, usually copper, that allows the bullet to penetrate a target more easily. Wadcutter - The front of the bullet is flattened.
Butt - The portion of the gun that is held or shouldered.
Caliber - In Firearms, the diameter of the bore measured from land to land, usually expressed in hundredths of an inch (.22 cal) or in millimeters (9mm). In ammunition, a naming system that indicates cartridge dimensions as well as bore diameters, and can be the same as the Firearm caliber.
Carbine - A general term referring to relatively short-barreled, quick-handling rifle.
Cartridge - A unit of ammunition, made up of a cartridge case, primer, powder, and bullet. Also called a "round", or “load”. Sometimes incorrectly called a “bullet”.
Cartridge case - The container for all the other components that comprise a cartridge. Sometimes incorrectly called a shell, shell casing, brass, or a hull.
Centerfire - The cartridge contains the primer in the center of the case head or base, where it can be struck by the firing pin of the action.
Chamber - The portion of the action that holds the cartridge ready for firing.
Cock - Place a firing mechanism (i.e. hammer, or firing pin) under spring tension prior to firing
Cylinder - Part of a revolver that holds ammunition in individual chambers that are rotated in turn into firing position.
Discharge - To cause a firearm to fire.
Double-action - Pulling the trigger both cocks the hammer and fires the firearm.
Ejector - The mechanism on a firearm which ejects or expels a cartridge or cartridge case from a firearm.
Extractor - The mechanism on a firearm that withdraws a cartridge or cartridge case from the chamber of a firearm.
Firearm - An assembly of a barrel and action from which a projectile(s) is discharged by means of a rapidly burning propellant. Also called a weapon, gun, handgun, long gun, pistol, revolver, etc.
Feed Ramp - An inclined, polished area on a repeating firearm, just behind the chamber, that helps guide a cartridge into the chamber when pushed forward by the closing bolt.
Firing Pin - That part of a firearm mechanism that strikes the primer of a cartridge to initiate ignition. Also called a striker.
Fluted Barrel - A rifle or pistol barrel, often of octagonal cross-section, into which longitudinal grooves have been milled. Fluted barrels, while more expensive to make than round barrels, dissipate heat more rapidly and they provide a better stifness-to-weight ratio.
Hammer - The part of a gun lock, which driven by a spring and released by a pull of the trigger, falls and (usually via an intervening firing pin) strikes the detonating primer of the load and discharges the gun. Hammers may be external or internal.
Hammerless - A firearm with its hammer enclosed inside the action body; ie. no visible hammer.
Magazine - This is a device for storing cartridges in a repeating firearm for loading into the chamber. It has a spring and follower to feed those cartridges into the chamber of a firearm. The magazine may be detachable or an integral part of the firearm. Also referred to as a "clip"
Magnum - An improved version of a standard cartridge that uses the same caliber and bullet, but has more powder (generally in a longer cartridge case), giving the fired bullet more energy. Magnum shotgun loads, however, refer to an increased amount of shot pellets in the shell.
Muzzle - The end of the barrel out of which the bullet comes.
Muzzle Brake - A fitting attached to the muzzle of a firearm, with a series of perforations designed to deflect some of the forward-rushing gasses and pull the firearm forward off the shoulder, reducing recoil.
Pistol - Another name for a handgun that does not have a revolving cylinder, the chamber is part of the barrel.
Ported barrels - Barrels with a series of holes or slots drilled near the muzzle. When a ported barrel is discharged, gasses moving violently down the barrel hit the forward edge of the holes and pull the gun forward off the shoulder, reducing felt recoil. Porting holes, when cut along the top of the barrel also work to depress the barrel under discharge, counteracting muzzle jump.
Primer - An explosive substance that ignites when struck to detonate the powder in a cartridge. Rimfire cartridges have a primer mixture crimped inside the base, while centerfire cartridges have a primer mixture in a ‘cup’ in the middle of the base of the cartridge case.
Receiver - The basic unit of a firearm which houses the firing and breech mechanism and to which the barrel and stock are assembled.
Reticle - A matrix of dots, posts or lines, visible inside a rifle's telescopic sight, normally adjustable via exterior knobs for wind and elevation.
Revolver - Handgun that has a cylinder with holes to contain the cartridges. The cylinder revolves to bring the cartridge into position to be fired. This is "single-action" when the hammer must be cocked before the trigger can fire the weapon. It is "double-action" when pulling the trigger both cocks and fires the gun.
Rifle - A firearm having rifling in the bore and designed to be fired from the shoulder. Also called a long gun.
Rifling - The spiral grooves cut or swaged inside a gun barrel that gives the bullet a spinning motion. The metal between the grooves is called a "land". The spiral can have either a left or right twist.
Rimfire - The cartridge has the primer distributed around the periphery of the base.
Round - An Alternate term for a cartridge.
Safety - A device, incorporated into the design of most firearms actions that, when engaged, should prevent the discharge of the firearm. Remember the general rules of responsible gun handling and never point a gun in a direction you do not intend to shoot.
Semi-Automatic - A type of firearm which, utilizing some of the recoil or some of the expanding-gas energy from the firing cartridge, cycles the action to eject the spent shell, to chamber a fresh one from a magazine and to cock the mainspring, placing the gun in position for another shot with nothing more needing to be done than to provide another pull on the trigger. Often erroneously referred to as automatic---but automatic actually refers to a machine gun.
Shotgun - A shoulder fired (long gun) with a smoothbore designed to fire shot shells containing numerous pellets or sometimes a single projectile.
Sights - The devices on top of a barrel that allow the gun to be aimed.
Silencer - A device that fits over the muzzle of the barrel to muffle the sound of a gunshot. Most work by baffling the escape of gases. Also known as a suppressor .
Single-action - The hammer must be manually cocked before the trigger can be pulled to fire the gun.
Slug - A term applied to a single projectile loaded into a shot shell.
Single Action - An action type, typical on handguns, where the hammer must be cocked manually prior to each shot if it is a revolver or prior to the first shot with an already loaded chamber and de-cocked hammer if it is a semi-automatic.
Snap Caps - Dummy cartridges with spring-loaded "primers" used to test the mechanical functioning of a firearm, particularly the trigger pulls, hammer-fall and ejector-timing of a break-open gun. It is not advisable to dry-fire a break-open gun on an empty chamber. Hardened steel parts can shatter without the soft brass primer to act as a shock absorber. Snap caps cushion the blow of the hammer and firing-pin when the use of a live cartridge would be impractical.
Trigger - That part of a firearm mechanism that is moved manually to cause the firearm to discharge.