General-purpose machine gun

A general-purpose machine gun (GPMG) is a belt-fed weapon used in a variety of roles, from bipod- or tripod-mounted infantry support to deployment as a helicopter door gun or a vehicle-mounted support weapon. It can provide fire support for vehicles or infantry from a variety of mounts.

In modern practice, it is an air-cooled medium machine gun, firing rifle cartridges such as the 7.62×51mm NATO, 7.62×54mmR, or 7.92x57mm Mauser. It is generally operated from a stationary position from either a bipod or tripod, or otherwise mounted on a vehicle, as it is usually too powerful and heavy to be fired effectively on foot from an unsupported standing position or on the move.

The GPMG barrel can be removed and replaced within seconds - in use, the barrel quickly heats up, necessitating its replacement after 200-400 rounds of continuous fire; once cooled down, the barrel can be reused.

History
The first general purpose machine gun was proposed by Vladimir Fyodorov in the early 1920. Ten years later the idea resurfaced in Denmark and Czechoslovakia, some time later - in Germany. "In 1934 the Germans adopted the MG 34. The MG 42, that succeeded it at the end of 1942, had better-functioning automatics and was cheaper to manufacture, but neither did the MG-42 meet the requirements of the army, which is evident from the continuous work on its improvement. The rapid attempt to modernize the system in 1945 had no practical significance whatsoever due to the end of WW2." The concept was successful enough to be adopted in many post-WWII armies.

Ironically, the Soviet Union was among the last to unify its light and heavy 7.62 mm machine guns. This only happened in the early 1960s, with the introduction of the PK machine gun, which replaced both the RP-46 (light/company machine gun) and the SGM (heavy/battalion machine gun).

Notable post-WWII examples

 * Belgian FN MAG, the most widely used GPMG among NATO and other western armies.
 * French AA-52, used in African countries.
 * American M60 (later replaced by the M240 (an FN MAG variant) in US service).
 * German MG3, a direct descendant of the MG 42, is still in service with the German Army and others.
 * Russian PK/PKM family of multi-purpose machine-guns, widely exported.
 * People's Republic of China, the Type 67 and later improved models.
 * South African Vektor SS-77.