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.

Ammunition in which the propellant is encased in a combustible or consumable material, eliminating the traditional metal cartridge case.

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.