They also usually have either a barrel cooling system, slow-heating heavyweight barrel, or removable barrels which allow a hot barrel to be replaced.Īlthough subdivided into " light", " medium", " heavy" or " general-purpose", even the lightest machine guns tend to be substantially larger and heavier than standard infantry arms. Because they become very hot, the great majority of designs fire from an open bolt, to permit air cooling from the breech between bursts. Some machine guns have in practice sustained fire almost continuously for hours other automatic weapons overheat after less than a minute of use. They are commonly mounted on fast attack vehicles such as technicals to provide heavy mobile firepower, armored vehicles such as tanks for engaging targets too small to justify the use of the primary weaponry or too fast to effectively engage with it, and on aircraft as defensive armament or for strafing ground targets, though on fighter aircraft true machine guns have mostly been supplanted by large-caliber rotary guns. Machine guns are used against infantry, low-flying aircraft, small boats and lightly/un armored land vehicles, and can provide suppressive fire (either directly or indirectly) or enforce area denial over a sector of land with grazing fire.
Nowadays, the term is restricted to relatively heavy crew-served weapons, able to provide continuous or frequent bursts of automatic fire for as long as ammunition feeding is replete. Unlike semi-automatic firearms, which require one trigger pull per round fired, a machine gun is designed to continue firing for as long as the trigger is held down. Many machine guns also use belt feeding and open bolt operation, features not normally found on other infantry repeating firearms.Ī vehicle with a Sumitomo M2 heavy machine gun mounted at the rear Similar automatic firearms of greater than 20 mm (0.79 in) caliber are classified as autocannons, rather than machine guns.Īs a class of military kinetic projectile weapon, machine guns are designed to be mainly used as infantry support weapons and generally used when attached to a bipod or tripod, a fixed mount or a heavy weapons platform for stability against recoils.
Submachine guns, which are capable of continuous rapid fire but using handgun cartridges, are also not technically regarded as true machine guns. Squad automatic weapons, which fire the same (usually intermediate-powered) cartridge used by the other riflemen from the same combat unit, are functionally light machine guns though not called so. Other automatic firearms such as assault rifles and automatic rifles are typically designed more for firing short bursts rather than continuous firepower, and not considered machine guns. 50 caliber M2 machine gun: John Browning's design has been one of the longest-serving and most successful machine gun designsĪ machine gun is an auto-firing, rifled long-barrel autoloading firearm designed for sustained direct fire with fully powered cartridges.