A firearm feed system where ammunition is stored in a flexible or rigid container (magazine) inserted into the grip or attached externally, feeding rounds into the chamber via a spring or follower.

Firearm action type where expanding gas from a fired cartridge cycles the mechanism, typically via a piston or direct impingement.

Uses high-pressure gas to cycle the action, rather than recoil energy.

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