The Gatling gun was designed by the American inventor Dr. Richard J. Gatling in 1861 and patented November 4, 1862. Gatling wrote that he created it to reduce the size of armies and so reduce the number of deaths by combat and disease, and to show how futile war is.

The Gatling gun was hand-crank operated with six barrels revolving around a central shaft, although some models had as many as ten. Early models had a fibrous matting stuffed in among the barrels which could be soaked with water to cool the barrels down. Later models eliminated the matting-filled barrels as being counterproductive.

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire bullets in quick succession from an ammunition belt or magazine, typically at a rate of several hundred rounds per minute.

The mechanism of the Maxim gun employed one of the earliest recoil operated firing systems in history. The idea is that the energy from the recoil is used, in lieu of a locked bolt or a lever mechanism, to eject each spent cartridge and insert the next one. This made it vastly more efficient and less labour intensive than previous rapid-firing guns, such as the Gatling, Gardner, or Nordenfelt guns that relied on actual mechanical cranking, as well as decreasing the gas buildup in the barrel, allowing the gun to fire more bullets over an extended period of time without overheating the barrel. The Maxim gun design still required water cooling, however, which gave it additional points of failure and made it more difficult to operate and heavier per calibre, compared to most later heavy machine guns.

The M1917 Browning machine gun is a heavy machine gun used by the United States armed forces in World War I, World War II, Korea, and to a limited extent in Vietnam, and by other nations. It was a belt-fed water-cooled machine gun that served alongside the much lighter air-cooled Browning M1919. It was used at the battalion level, and often mounted on vehicles (such as a jeep). There were two main iterations of it: the M1917, which was used in World War I; and the M1917A1; which was used thereafter. The M1917 was used on the ground and on some aircraft, and had a firing rate of 450 round/min; the M1917A1 had a firing rate of 450 to 600 round/min.

The M60, officially the United States Machine Gun, Caliber 7.62 mm, M60, is a family of American general-purpose machine guns firing 7.62×51mm NATO cartridges from a disintegrating belt of M13 links. There are several types of live ammunition approved for use in the M60, including ball, tracer, and armor-piercing rounds.
Introduced in 1957, it has served with every branch of the U.S. military and still serves with other armed forces. Its manufacture and continued upgrade for military and commercial purchase continues into the 21st century, though it has been replaced or supplemented in most roles by other designs, notably the M240 in U.S. service.

The M134 Minigun is a 7.62x51 mm NATO, six-barreled machine gun with a high rate of fire (2,000 to 6,000 rounds per minute). It features Gatling-style rotating barrels with an external power source, normally an electric motor. The "Mini" of the name is in comparison to designs that use a similar firing mechanism but larger shells, such as General Electric's earlier 20-millimeter M61 Vulcan, and "gun" for a caliber size smaller than that of a cannon, typically 20 mm and higher.
"Minigun" refers to a specific model of weapon that General Electric originally produced, but the term "minigun" has popularly come to refer to any externally powered Gatling gun of rifle caliber. The term is also used to refer to guns of similar rates of fire and configuration regardless of power source and caliber.