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.

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.

Select fire is a fire selector mechanism on a firearm that lets the shooter choose the firing mode, such as semi‑automatic, burst, or fully automatic.