III.

Types of Machine Guns

Machine guns are grouped into four general categories: light machine guns; general-purpose, or medium, machine guns; heavy machine guns; and externally powered machine guns.

A.

Light Machine Guns

Light machine guns use ammunition of .30 caliber (7.62 mm) or less and are designed to have minimum weight so that a single soldier may use them. The United States M249 Squad Automatic Weapon (SAW) is a portable, lightweight machine gun that fires 5.56-mm ammunition from continuous linked belts, or from linked ammunition contained in large-capacity magazines. The SAW is light enough to be operated by one soldier, but it can fire for longer periods of time than an automatic rifle. The SAW replaced the older U.S. M60 machine gun, which weighed nearly twice as much as the SAW.

B.

Medium Machine Guns

General-purpose, or medium, machine guns ordinarily use 7.62-mm ammunition. They are used for firing at more distant targets than light machine guns and can fire for longer periods of time. Medium machine guns are also heavier, requiring teams of at least two soldiers to use them. A medium machine gun requires a tripod (three-legged stand) for support, or a mounting bracket if used on a vehicle. The M60 served as a general-purpose machine gun for many years in the U.S. Army. It could be fired from a bipod (two-legged stand), from a tripod, from a vehicle, or from the side of a helicopter. Beginning in the 1980s, the M60 was gradually replaced by newer, more improved machine guns such as the M240. It can fire 700 to 1,000 rounds per minute and is more durable and reliable than the M60.

C.

Heavy Machine Guns

Heavy machine guns fire .50-caliber (12.7-mm) or larger ammunition and generally require a crew. Heavy machine guns can deliver concentrated and devastating firepower. They often serve as the main armament on land combat vehicles and on some aircraft. The M2 heavy machine gun, designed by American inventor John Moses Browning, was first built at the end of World War I (1914-1918). With some modifications, it still serves in the U.S. military and in other armies of the world. Another type of heavy machine gun is the U.S. Mark 19 machine gun, which fires 40-mm grenades. The grenades explode upon impact, making the weapon useful against both armored targets and enemy soldiers.

D.

Externally Powered Machine Guns

Externally powered weapons are found in many military aircraft, in some vehicles, and in antiaircraft units on the ground or aboard naval vessels. Many externally powered machine guns are modern motorized versions of the hand-turned Gatling gun, patented by American inventor Richard Jordan Gatling in 1862. Gatling guns feature several barrels that rotate around a central shaft. Gatling guns can achieve high rates of fire without overheating. The 30-mm Gatling gun on the A-10 Thunderbolt II attack aircraft can fire 3,900 rounds a minute and is capable of destroying armored targets such as tanks.