Glossary of Firearms Terms

We've brought together the important terms you'll need to know when discussing firearms.
Accidental Discharge (AD)
The unintentional discharge of a firearm. The causes can be the accidental fingering of the trigger, the dropping of a firearm without an internal drop safety, or a malfunction of the firearm. An accidental discharge cannot practically occur without an ammunition round in the chamber.
See also this Wikipedia article.
Actions
The physical mechanism and the method by which cartridges are loaded, locked, and extracted from the firearm.
See also this Wikipedia article.
Air gun
Like a firearm; can be a pistol, rifle, or shotgun; but unlike a firearm, expels the projectile by means of compressed gas instead of an explosion of propellant.
See also this Wikipedia article.
Ammunition
The assembled package of the casing, the bullet, the propellent (typically gunpowder), and the primer.
See also this Wikipedia article.
Barrel
The metal tube down which the bullet travels to exit a firearm.
See also this Wikipedia article.
Bolt
Blocks the rear end of the barrel, and includes the firing pin.
See also this Wikipedia article.
Break-action
One of the kinds of firearms in which the barrel is hinged to expose the breech. The process of preparing the firearm for the next round of ammunition is done by "breaking" open the barrel and manually loading a new round.
See also this Wikipedia article.
Breech
The rear part of the barrel which opens for ammunition loading in modern day firearms.
See also this Wikipedia article.
Bullet
The projectile expelled from the firearm.
See also this Wikipedia article.
Caliber
The approximate diameter of the bore of the firearm barrel, which is also the approximate diameter of the outside of the bullet.
See also this Wikipedia article.
Cartridge
See Ammunition.
Casing
The metalic case in which the primer, gunpowder, and bullet are package.
See also this Wikipedia article.
Centerfire ammunition
Ammunition cartridge in which the primer is located in the middle of the base of the casing.
See also this Wikipedia article.
Chamber
The rearward part of the barrel in which the ammunition is loaded.
See also this Wikipedia article.
Cocked
For a firearm with either a single or double action trigger, the hammer has been pulled back into its single action point (ready for the hammer to drop).
Condition
Condition is a number and refers to the number of steps necessary to make the firearm ready to discharge.
See also this Wikipedia article.
Discharge
The act of firing a firearm, whether intentionally or not.
Double Action/Single Action Trigger
A trigger that is double action for the first shot and single action for all subsequent shots.
See also this Wikipedia article.
Double Action Only Trigger
A trigger that only allows a double action pull.
See also this Wikipedia article.
Double Action Trigger
A trigger that both raises the hammer or striker and then drops the hammer or striker.
See also this Wikipedia article.
Extractor
Removes and ejects the case of the ammunition from the barrel.
See also this Wikipedia article.
Firearm
A handheld weapon that expels a small projectile at high speed through a controlled explosion.
See also this Wikipedia article.
Firing pin
Strikes the primer of the ammunition to initiate the explosion to fire a firearm.
See also this Wikipedia article.
Follower
In semi-automatic firearms, it is the sliding part of the magazine, that holds the spring into the magazine, and which follows the last round of ammunition. The follower has a shape that is specific to the caliber of ammunition. In double-stack magazines, the follower has the shape of one round of ammunition offset to one side so that the ammunition will load into the magazine in the alternating pattern.
See also this Wikipedia article.
Frame
The part of the firearm that contains the trigger mechanism. The frame *is* the firearm; all other firearms parts (barrel, trigger, etc.) are just accessories.
Gunpowder
The explosive powder that acts as the propelant for the bullet..
See also this Wikipedia article.
Hollow-point bullet
A bullet with a hollowed-out tip, causing the bullet to expand when it enters its target, to cause more damage to the target and less chance of over-penetration.
See also this Wikipedia article.
Jacketing
Jacketing is the wrapping of the bullet in a different metal, such as brass, copper, or an alloy.
See also this Wikipedia article.
Magazine
In semi-automatic firearms, it is the detachable container that holds multiple rounds of ammunition. The magazine is specific to the type of firearm.
See also this Wikipedia article.
Muzzle
The end of the barrel from which the projectile will exit when the firearm is discharged..
See also this Wikipedia article.
Muzzle flash
The visible flash of light that is released from the muzzle of the firearm as it is discharged and the projectile leaves the barrel.
See also this Wikipedia article.
Muzzle velocity
The speed at which the bullet leaves the muzzle of the firearm’s barrel.
See also this Wikipedia article.
Overpressure Ammunition
Ammunition that has a higher internal pressure for the purpose of increasing muzzle velocity and stopping power (terminal balistics), typically for the purpose of self defense.
See also this Wikipedia article.

Pistol
A firearm designed to be fired from one hand.
See also this Wikipedia article.
Porting
Porting is a aspect of the barrel where slots are created in the top of the barrel near the muzzle. Those slots allow the expanding gases from the firearms discharge to escape upward as the bullet approaches the muzzle, thereby creating a force downward to counter the recoil created by the discharge.
Primer
The small, circular button at the base of the ammunition casing, filled with nitro glycerin, when struck, explodes.
Pump-action
One of the kinds of rifles and shotguns in which the process of cycling the firearm for the next round of ammunition is done by a pumping action on the grip under the rifle barrel.
See also this Wikipedia article.
Rack
To manually cycle a semi-automatic firearm to load a round of ammunition into the chamber.
Receiver
The part of the firearm that contains the operating parts. .
See also this Wikipedia article.
Recoil
The backward kick caused by the explosion expelling the projectile. Heavier guns—those with longer barrels—will have less perceived recoil using the same ammunition as lighter guns.
See also this Wikipedia article.
Report
The sound of the firearm discharging.
Rifle
A firearm with a long barrel that is discharged while the operator supports the firearm from the shoulder.
See also this Wikipedia article.
Rifling
The grooves that spiral down the inside of the barrel and which impart the spin on the bullet so that it will fly straight.
See also this Wikipedia article.
Rimfire ammunition
An ammunition cartridge in which the priming compound is contained around the inside of the rim of the cartridge.
See also this Wikipedia article.
Shotgun
A rifle that fires a casing full of shot pellets.
See also this Wikipedia article.
Silencer
This doesn't exist; see Suppressor.
Single Action Trigger
A the trigger only allows the hammer or striker to fall.
See also this Wikipedia article.
Stopping power
The ability of the ammunition to incapacitate the target where it stands.
See also this Wikipedia article.
Suppressor
Working exactly like a car exhaust muffler does, it muffles the report of a firearm discharging.
Trigger
The mechanism that operates the hammer or striker to discharge the firearm.
See also this Wikipedia article.