Heavy Machine Gun

The heavy machine gun or HMG is a larger class of machine gun generally recognized to refer to two separate stages of machine gun development.

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 British inventor Hiram Maxim. 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).

The modern definition refers to a class of large-caliber (generally .50 or 12.7mm) machine guns, pioneered by Vasily Degtyaryov and John Moses Browning with the DShK and M2 machine gun. These weapons are 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. In this sense, the "heavy" aspect of the weapon refers to its superior power and range over light- and medium-caliber weapons, in addition to its weight. This class of machine gun came into widespread use during World War II, when the M2 was used widely in fortifications, on vehicles and in aircraft by American forces. A similar HMG capacity was fielded by the Soviets in the form of the DShK in 12.7x108mm. The ubiquitous German MG42 general-purpose machine gun, though well-suited against infantry, lacked the M2's anti-fortification and anti-vehicle capability, a fact that was noted and lamented by the Germans. The continued need for a longer-range machine gun with anti-materiel capability to bridge the gap between exclusively anti-infantry weapons and exclusively anti-materiel weapons has led to the widespread adoption and modernization of the class, and most nations' armed forces are equipped with some type of HMG.

Currently, firearms with calibers smaller than 12.7 mm are generally considered medium or light machine guns, while those larger than 15 mm are generally classified as autocannons instead of heavy machine guns.