Page "Machine gun" Paragraph 32

Firing a machine gun produces great amounts of heat.

In a worst-case scenario this may cause a cartridge to fire even when the trigger is not pulled, potentially leading to damage or causing the gun to cycle its action and keep firing until it has exhausted its ammunition supply or jammed.

To prevent this, some kind of cooling system is required.

Early heavy machine guns were often water-cooled ; while very effective, the water also added considerable weight to an already bulky design.

Air-cooled machine guns feature quick-change barrels, often carried by a crew member.

The higher the rate of fire, the more often barrels must be changed and allowed to cool.

To minimize this, most air-cooled guns are fired only in short bursts or at a reduced rate of fire.

Some designs-such as the many variants of the MG42-are capable of rates of fire in excess of 1500 rounds per minute.