Bolt – A mass of metal that feeds the round from the magazine into the chamber and support it during firing.
Bolt-Action – The locking mechanism that works much like a deadbolt on a door. The user lifts the bolt handle, pulls it back, then pushes it forward and turns the handle down.
Bore – The inside of the barrel of a gun excluding the chamber. It is the channel through which projectile passes when the gun is discharged.
Breech – The open rear part in a gun where ammunition is loaded.
Cartridge – A self-contained unit, comprising case, powder, primer and bullet. Each cartridge can be fed into the chamber, discharged, and the empty one extracted.
Chamber – Portion of the gun where the round is inserted before it is able to be fired.
Ejection Port – An opening in a firearm receiver where expended round shells are ejected from a gun.
Firing Pin – A tiny, rounded piece designed to strike the primer of a round. This detonates the bullet and begins propelling a round down the barrel.
Hammer – The part of a firearm that is used to strike the firing pin, which then ignites the charge in a round of ammunition.
Magazine – Ammunition feeding device attached to certain firearms.
Slide – The fixed, top part of a semi-automatic pistol that moves while a round is fired. The slide acts as the bolt, and houses the firing pin.
Trigger – Mechanism located underneath a gun that, when pulled, begins the firing sequence. This is usually surrounded by a thin strip of metal called a trigger guard.