Machine gun

A machine gun is a 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.

In United States law, machine gun is a term of art for any fully-automatic firearm, and also for any component or part that will modify an existing firearm into a fully-automatic firearm.

Operating principles

There have been two main machine gun eras: the era of manual machine guns and the era of mason machine guns. The technical development itself is marked by a series of developments of specific automatic features, as well as technical developments (such as linked ammunition). The era of manual multi-shot devices extends back hundreds of years (such as manual volley guns), but the development of manual and automatic machine guns takes place almost entirely in the latter half of the 1800s. Manual machine guns are manually-powered, e.g., a crank must be turned to power reloading and firing, as opposed to simply holding down a trigger, as with automatic machine guns. There are many other notable features, but this is one of the most significant to allowing higher rates of fire common to machine guns.

Manual machine guns, as well as manual volley guns, saw their first major use in the American Civil War. The Gatling gun and "coffee gun" both used manually-powered automatic loading, fed via a hopper filled with cartridges. The Gatling gun would be the major type of the late 19th century, though there were many other manual designs with varying degrees of use (e.g. the Nordenfelt gun). The first automatic machine gun was the recoil-operated Maxim gun, which used linked (belt) ammunition, as well as a single barrel and automatic loading. This concept of using bullet energy would also drive the development of nearly all other semi and fully automatic firearms of 20th century.

The two major operation systems of modern automatic machine guns are gas operation and recoil operation. As the name implies, the gas operated system uses the gas generated from the burning powder to cycle the action, whereas the recoil operated uses the recoil generated from the ejecting bullet. The first gas-operated machine gun was the Colt-Browning M1895.. It was followed shortly thereafter, in 1897, by the gas-operated Hotchkiss machine gun.

Another (minor) type is the externally-powered machine gun. Rather than human manual power or energy generated by the cartridge, an external source such as an electric motor is used. These types are now called by more specific names such as Minigun and Chain gun. They are common on fighting aircraft and ground vehicles, where the externally powered mechanism allows for automatic clearing of many failure conditions that would otherwise disable the firearm.