A machine gun is a crew-served, fully-automatic mounted or portable firearm, usually designed to fire rifle cartridges in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute. The first machine guns were manually operated, for example, by turning a hand crank.
Machine guns are generally categorized as submachine guns, machine guns, or autocannons. The distinction between submachine guns and machine guns is subtle, hinging upon whether the ammunition used is intended for use in side arms (chiefly semi-automatic pistols) or rifles; the difference between machine guns and autocannons is based on caliber, with autocannons using calibers equal to and larger than about 20mm.
Unlike semi-automatic firearms, which require one trigger pull per bullet fired, a machine gun is designed to fire bullets as long as the trigger is held down and ammunition is fed into the weapon. Although the term "machine gun" is often used by civilians to describe all fully automatic weapons, in military usage the term is restricted to relatively heavy, crew-served, weapons fired from some sort of support rather than hand-held, able to provide continuous or frequent bursts of automatic fire for as long as ammunition lasts. Machine guns are normally used against unprotected or lightly-protected personnel, or to provide suppressive fire.
The General Purpose Machine Gun (GPMG), such as the AA-52 and FN MAG, are carried and fired by one man, However, the he is only ONE of 3 or 4 people required to support and operate the weapon system. The team usually consists of the gunner, assistant gunner and 1 or 2 "mules".
The gunner carries the gun, his personal weapon (usually a sidearm) and equipment and 3 "bandoliers" of ammo. These "bandoleers" are bags containing 150 to 200 rounds of linked ammo each.
The assistant gunner is carrying the accessory bag, containing the spare barrel, cleaning kit and tools to maintain the weapon. He is also carrying his personal equipment, personal weapon,(usually a sidearm) and 3 bandoleers of ammo.
The third team member is carrying his personal weapon(a rifle), his personal equipment, the tripod for the gun and 3 bandoliers of ammo.
The fourth team member carries his personal weapon (a rifle) and equipment and 3 bandoliers.
When a position for the gun has been selected, usually by the squad leader, #3 man places the tripod in position and moves off to one side, taking up a position to cover that flank. The #4 man takes a position on the opposite side to cover that flank.
The gunner steps up and mounts the gun in the tripod and takes a position behind the gun.
The assistant gunner sets the accessory bag down and takes his position on the left side of the gun, helping the gunner load the gun and prepared to keep the ammo ready.