US Navy Boat Team crewman firing a heavy machine gun. Note defensive armor and ammo belt; spent cartridges dropping. Crewman in camouflaged outfit, radio equipment, camera on helmet, submachine gun over his shoulder

A U.S. Navy 7.62 mm GAU-17/A Minigun. It has an electric motor on top which does the loading, priming, and firing. Note the rapid cartridge case ejection

A machine gun is a weapon that can fire one bullet after another as long as the trigger is pulled and there are bullets ready to fire. This is called automatic fire. A more general name for this type of weapon is an automatic weapon. Machine guns fire bullets delivered from a long chain of cartridges called an ammunition ('ammo') belt, or use spring-loaded boxes called magazines. Machine guns are usually divided into heavy-duty machine guns, light machine guns, and sub-machine guns.