A type of firearm action where the breech is not locked and the cartridge case expands to seal the breech, using case expansion and pressure to retain gases.

A firearm feed system where ammunition is stored in a separate container (magazine) that can be removed and replaced, enabling rapid reloading.

Adjustable metal aiming devices on firearms, consisting of a front post and rear notch, used without magnification.

A pistol barrel with external helical grooves allowing the attachment of a suppressor or other muzzle devices.