Heavy machine-gun

The heavy machine gun or HMG is a class of machine gun implying greater characteristics than medium machine guns.

There are two generally recognized classes of weapons identified as heavy machine guns. The first is weapons from World War I identified as "heavy" due to the weight and encumberment of the weapons themselves. The second is large-caliber (generally .50 or 12.7mm) machine guns, pioneered by John Moses Browning with the M2 machine gun, designed to provide increased range, penetration and destructive power against vehicles, buildings, aircraft and light fortifications beyond the standard rifle calibers used in medium or general-purpose machine guns, or the intermediate cartridges used in light machine guns.

The term was originally used to refer to the generation of machine guns which came into widespread use in World War I. These fired standard rifle cartridges such as the 7.92 Mauser, .303 British or 7.62×54mmR, but featured heavy construction, elaborate mountings, and water-cooling mechanisms that enabled long-range sustained automatic fire with excellent accuracy. However, these advantages came at the cost of being too cumbersome to move quickly, as well as requiring a crew of several soldiers to operate them. Thus, in this sense, the "heavy" aspect of the weapon referred to the weapon's bulk and ability to sustain fire, not the cartridge caliber. This class of weapons was best exemplified by the Maxim gun, invented by the American inventor Hiram Maxim, who had traveled to England to market his design and became a British subject in 1900. The Maxim was the most ubiquitous machine gun of World War I, variants of which were fielded simultaneously by three separate warring nations (Germany with the MG 08, Britain with the Vickers, and Russia with the PM M1910).

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