An ammunition belt is a firearm device used to package and feed cartridges, typically for rapid-firing automatic weapons such as machine guns. Belt-fed systems minimize the proportional weight of the ammunition apparatus to the entire weapon system, and allow high rates of continuous fire without needing frequent magazine changes. The capacity of belts and associated belt containers is typically a function of weight and bulk, and their size is limited by caliber and the combined portability of the weapon and ammunition. Typical capacities for man-portable weapon systems range from 50 to 300 rounds of ammunition.

An automatic firearm or fully automatic firearm is an autoloading firearm that continuously chambers and fires rounds when the trigger mechanism is actuated. The action of an automatic firearm is capable of harvesting the excess energy released from a previous discharge to feed a new ammunition round into the chamber, and then igniting the propellant and discharging the projectile by delivering a hammer or striker impact on the primer.