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Automatic Colt Pistol, a type of ammunition.

• Action

The mechanism of a firearm involved with presenting the cartridge for firing, and in removing the spent casing and introducing a fresh cartridge.


A firearm which continues to fire as long as the trigger remains depressed.

• Backstrap

The rear of two gripstraps on a handgun, which lies beneath the heel of the hand when gripping the gun.

• Ball

A military term for standard, full metal jacketed ammunition.

• Ballistics

The science of cartridge discharge and the bullet’s flight.

• Barrel

The long tubular cylindrical part of a firearm, bored out to provide an exit path for the discharging bullet. The barrel serves the purpose of providing direction and velocity to the bullet.

• Blowback

A semi-automatic firearm whose breechblock and barrel are not mechanically locked together when fired. In such case the breechblock immediately begins to separate from the barrel upon firing. Blowback is used in comparatively low powered weapons, in which inertia of the breechblock, and cartridge wall adhesion against the chamber, are sufficient enough to retard opening until breech gas pressures have fallen to a safe level.

• Bluing

The chemical process of artificial oxidation (rusting) applied to gun parts so that the metal attains a dark blue or nearly black appearance.

• Bore

The interior of a gun barrel.

• Bore Diameter

The diameter of the inside of the barrel after boring, but before rifling. The land-to-land diameter.

• Bottle Necked

A type of cartridge whose bullet diameter is substantially less than the body diameter of the casing.

• Breech

That portion of the gun that contains the rear chamber portion of the barrel, action, trigger or firing mechanism, and the magazine.

• Breechblock

The part of the weapon that seals the rear of the chamber and supports the casehead when the cartridge is fired. Breechloading firearms are classified according to the type of action used, the mechanical means of locking it into place for firing and displacing it for reloading. i.e. “Blowback”, “Delayed Blowback”, and “Recoil” operated actions.

• Bull Barrel

A heavier, thicker than normal barrel with little or no taper.

• Bullet

The metal projectile, typically in the shape of a pointed cylinder, expelled from the mouth of a firing cartridge.

• Caliber

The diameter of the bore of a barrel measured from land to land, usually measured in tenths of an inch or in millimeters. It does not designate the actual diameter of a bullet.

• Cannelure

A groove or indention around the circumference of a bullet. Its purpose is to permit the cartridge casing to be crimped tightly against the bullet shank to hold it firmly to the casing. A groove or indention around the circumference of a bullet. Its purpose is to permit the cartridge casing to be crimped tightly against the bullet shank to hold it firmly to the casing.

• Cartridge

In modern terms, a round of ammunition consisting of casing, primer, powder and projectile. In the “percussion-cap” era, the cartridge consisted of the projectile and powder in a paper packet, with the primer cap separate.

• Casing

A cylindrical tube closed at one end that holds the primer and powder of a cartridge. The cartridge bullet is crimped into the open end of the casing. They are typically made from brass, but can be steel, aluminum, or even plastic.

• Centerfire

A cartridge in which the primer or primer assembly is seated in a pocket or recess in the center of the base of the casing (the casing head). Also, refers to a firearm which uses centerfire cartridges.

• Chamber

The part of the firearm at the rear of the barrel that is reamed out so that it will contain a cartridge for firing.

• Chamber Throat

This is the area in the barrel that is directly forward of the chamber, which tapers to the bore diameter.

• Charger

A device typically made from stamped metal which holds a group of cartridges for easy and virtually simultaneous loading into the fixed magazine of a firearm.

• Clip

This term is often used when referring to a detachable magazine. But in fact, it is a device, usually of stamped metal similar to a charger that holds a group of cartridges, and is inserted along with the cartridges into certain magazines. It is expelled after the last round in the magazine is spent.

• Cock

The term referring to the action of manually drawing the hammer back against its spring until it becomes latched against the sear, or sometimes the trigger itself, arming the hammer to be released by a subsequent pull of the trigger.

• Cylinder

A rotating cartridge holder in a revolver. The cylinder also contains the chamber portion of the revolver. Cartridges are held, and fired, within the cylinder. Cartridge chambers are evenly placed around the axis of the cylinder. The cylinder has a linkage to the firing mechanism which rotates each chamber into alignment with the barrel prior to each firing.

• Cylinder Stop

On a revolver, a spring activated device housed in the bottom of the frame beneath the cylinder that engages alignment notches in the cylinder. It stops the cylinder’s rotation and holds it in place each time a chamber in the cylinder is in alignment with the barrel.

• Delayed Blowback

A self-loading firearm whose breechblock and barrel are not positively locked together, but which incorporates a mechanism which initially restricts the breechblock from moving when fired, delaying its opening.

• Double-Action (DA)

A revolver or pistol on which a long trigger pull can both cock and release the hammer to fire the weapon. In a revolver this action also rotates the cylinder to the next chambered round. Double-Action aslo implies a single-action stage which can cock the gun separately, alternately called Double Action/Single Action or DA/SA.

• Double-Action Only (DAO)

Typically on striker-fired pistols and spurless-hammer revolvers and referring to a trigger where the firing mechanism cannot be cocked in a single-action stage. Firing always occurs as a double-action sequence where pulling the trigger both cocks and then fires the gun.

• Dovetail

A flaring machined or hand-cut slot that is also slightly tapered toward one end. Cut into the upper surface of barrels and sometimes actions, the dovetail accepts a corresponding part on which the sight is mounted.

• Ejector

The part on the firearm whose function is to throw a spent casing from the gun after firing.

• Ejector Star

On a revolver, the collective ejector, manually operated through the center of an opened cylinder, when activated, clears all chambers at once.

• Extractor

On a pistol, a part, normally hooked or crescent shaped, attached to the breechblock, which withdraws the spent casing from the chamber when the breechblock separates from the barrel after firing.

• Firing Pin

In a hammer fired gun, this is a hardened pin housed in the breechblock, centered directly behind the primer cap of a chambered cartridge. When struck by the hammer it impacts the primer cap of the cartridge, discharging the weapon.

• Frame

The common part of a handgun to which the action, barrel and grip are connected.

• Front Strap

The part of a revolver or pistol grip frame that faces forward and often joins with the trigger guard.


Glock Auto Pistol, a type of ammunition.

• Grip

The handle used to hold a handgun. Often refers to the side-panels of the handle.

• Gripstraps

The exposed portion of a handgun’s frame, the front strap and backstrap, that provides the foundation for the handgun’s grip.

• Grooves

Spiral cuts into the bore of a barrel that give the bullet its spin or rotation as it moves down the barrel.

• Half Cock

A position of the hammer in a hammer-activated firing mechanism that acts as a manual safety.

• Hammer

That part of a revolver or pistol that impacts the firing pin or the cartridge directly, discharging the weapon. Its movement is rotational around its axis which is fixed to the frame.

• Hammer Spur

The thumbpiece on the top rear of the hammer that enables it to be manually drawn back to full cock.

• Hammerless

This general term can either refer to revolver or pistol designs that actually have hammers but are fully encased inside the frames, hammer designs where the spurs have been removed for concealment, or striker-fired pistols that are truly hammerless.

Hang Fire

Hang fire refers to an unexpected delay between the triggering of a firearm and the ignition of the propellant. Modern weapons are susceptible, particularly if the ammunition has been stored in an environment outside of the design specifications. A hang fire should be suspected whenever a weapon fails to fire, but has not clearly malfunctioned. In modern weapons it is more likely that the round is a "dud" (one that will never fire at all), but it is important not to immediately remove the round from the chamber. If a hang fire has in fact occurred, a round detonating outside of the weapon, or in a revolver chamber not aligned with the bore, could cause serious injury. If the operator believes that the weapon correctly cycled a fresh round and the action is not visibly jammed, the correct procedure is to keep the weapon pointed at a safe target for thirty seconds, if it does not fire, then remove and safely discard the defective round.


Hornady Magnum Rimfire, a type of ammunition.

• Lands

Raised portions of the bore left between the grooves of the rifling in the bore of a firearm. In rifling, the grooves are usually twice the width of the lands.

• LC

Long Colt, a type of ammunition.

• Long Recoil

A semi-automatic pistol in which the barrel and breechblock are locked together for the full distance of rearward recoil travel, after which the barrel returns forward, while the breechblock is held back. After the barrel has fully returned, the breechblock is released to fly forward, chambering a fresh round in the process.

• LR

Long Rifle, a type of ammunition.

• Magazine

A container, either fixed to a pistol’s frame or detachable, which holds cartridges under spring pressure to be fed into the gun’s chamber.

• Magnum

A modern cartridge with a higher-velocity/pressure load or heavier projectile than standard.

• Mainspring

Term often used for the hammer spring.

• Misfire

A condition when firing a gun in which the cartridge fails to discharge.

• Muzzle

The forward end of the barrel where the projectile exits.

• Muzzle Velocity

The speed of the bullet, measured in feet per second or meters per second, as it leaves the barrel.

• Neck

The constricted forward section of a bottle-necked cartridge casing – the portion that grips the bullet.

• Ogive

A type of curve represented by the curved section of a bullet between its bearing surface and its tip.

• Open Frame

Refers to a revolver frame that has no topstrap over the cylinder.

• Pistol

Refers generally to any handgun that is not a revolver. This includes self-loaders, manual repeaters, single-shots, double or multiple barrel pistols, derringers.

• Polygonal

Rifling without hard-edged lands or grooves, typically consisting of flat surfaces that meet at angles round the bore .

• Primer

A small detonating cap fitted in the head of a centerfire cartridge casing that, when struck by a firing pin, ignites the powder charge.

• Primer Pocket

The counter bore in the center of the base of a centerfire cartridge casing in which the primer assembly is seated.

• Primer Ring

Refers to a visible dark ring created by the primers in centerfire ammunition around the firing pin hole in the frame after much use.

• Receiver

In handguns, this refers to the frame.

• Recoil-Operated

Refers to a semi-automatic pistol whose barrel and breechblock both recoil rearward in reaction to the discharging bullet. See “Short recoil” and “Long recoil”.

• Rifling

Typically, a series of spiral grooves cut into the bore of the barrel. Rifling stabilizes the bullet in flight by causing it to spin. Rifling may rotate to the right or left. See “twist”.

• Rimfire

A self-contained metallic cartridge where the primer is contained inside the hollow rim of the cartridge case. The primer is detonated by the firing pin striking the outside edge of the rim, crushing the rim against the rear face of the barrel.

• Rimless

Refers to a cartridge in which the base diameter is the same as the body diameter. The casing will normally have an extraction groove machined around it near the base, creating a “rim” at the base that is the same diameter as the body diameter.

• Round

A unit of ammunition consisting of the primer, casing, propellant and bullet. A cartridge.

• Safety

A mechanical device built into a weapon intended to prevent accidental discharge. It may be either manually operated or automatic.

• Sear

A pivoting part of the firing mechanism of a gun, either part of the trigger or an intermediate piece, that catches and holds the hammer or striker at full cock. Pressure on the trigger causes the sear to release the hammer or striker, allowing it to strike the firing pin and discharge the weapon.

• Self-Loader

Another term for semi-automatic. More commonly refers to early designs of semi-automatic pistols.

• Semi-Automatic

A pistol that is loaded manually for the first round. Upon pulling the trigger, the gun fires. Energy from the discharging bullet is used to eject the fired round, cock the firing mechanism and feed a fresh round from the magazine. The trigger must be released after each shot and pulled again to fire the next round.

• Short Recoil

Refers to a semi-automatic pistol in which the barrel and breechblock are locked together for only a short distance of rearward recoil travel, at which point the two are uncoupled, the barrel is stopped and the breechblock continues rearward, extracting the spent casing from the chamber. Upon returning forward, the breechblock chambers a fresh round and forces the barrel back into its forward position. Most modern recoil operated semi-automatic pistols use short recoil.

• Single-Action (SA)

A pistol or revolver, in which the trigger is only used for firing the weapon, and cannot be used to cock the firing mechanism. On single-action revolvers, the hammer must be manually drawn back to full cock for each shot. On pistols, the recoil action will automatically recock the hammer for the second and subsequent shots.

• Slide

The upper portion of a semi-automatic pistol that houses the barrel and contains the breechblock and portions of the firing mechanism. As its name states, it slides along tracks in the top of the frame during the recoil process providing the linkage between the breechblock and barrel.

• Slide Lever

Typically refers to a lever either on the left or right side of a pistol’s frame that is used to release the slide for removal, maintenance and cleaning.

• Solid Frame

Refers to a revolver in which the cylinder window is cut into a single solid piece of frame stock. The construction is neither break-open nor open frame. This type of revolver is loaded be the cylinder flipping out of the solid frame, or by feeding individual rounds into exposed chambers that are rotated out to the side of the frame.

• Speed Loader

In revolvers in which the entire rear of the cylinder can be exposed for loading, the speed loader is a circular device or clip that holds a complete set of cartridges aligned to insert into all chambers of the cylinder simultaneously.

• Striker

In a handgun that does not have a hammer, the striker is a linear driven, spring loaded cylindrical part which strikes the primer of a chambered cartridge. The striker replaces both the hammer and firing pin found in hammer driven pistols.

Squib Load

A squib load is a firearms malfunction in which a fired projectile does not have enough force behind it to exit the barrel, and thus becomes stuck in the bore. This type of malfunction can be extremely dangerous, as failing to notice that the projectile has become stuck in the barrel may result in another round being fired directly into the obstructed barrel, resulting in a catastrophic failure of the weapon's structural integrity and the death or injury of the shooter.

• Topstrap

The part of a revolver frame that extends over the top of the cylinder and connects the top of the standing breech with the forward portion of the frame into which the barrel is mounted.

• Trajectory

The arc described by a projectile traveling from the muzzle to the point of impact.

• Trigger

Refers to the release device in the firing system that initiates the cartridge discharge. Usually a curved, grooved or serrated piece that is pulled rearward by the shooter’s finger, which then activates the hammer or striker.

• Trigger Bar

On a semi-automatic pistol, or any other firearm in which the trigger is at some distance from the sear, this is an intermediate piece connecting the two parts.

• Trigger Guard

Usually a circular or oval band of metal, horn or plastic that goes around the trigger to provide both protection and safety in shooting circumstances.

• Twist

The rate at which rifling grooves arc around the core of the barrel, measured in calibers, inches or centimeters. Twists can arc from left-to-right or right-to-left from the rear of the barrel. This is described as either a right-hand or left-hand twist.


Winchester Centerfire, a type of ammunition.


Winchester Magnum Rimfire, a type of ammunition.

Glossary of Firearm Terms
Glossary of Firearm Terms

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