For heavy machine gun (HMG or, from British Heavy Machine Gun) refers to a class of machine guns.
This term generally refers to two separate stages of the development of machine guns. Originally the term was referring to the first generation of machine guns which came into widespread use during the First World. These fired the standard rifle cartridge (~ .30 or7.62 mm), but they had a heavy construction, elaborate accessories, cooling water allowing for a sustained defensive fire, heavy and with excellent accuracy, but they were too bulky for they can move quickly. Thus, in this sense, the adjective “heavy” was reported to the mass of the weapon and the ability to fire supported, not to the caliber. This class of weapons is best represented by the Maxim machine gun, invented by the American Hiram Maxim. The was the most common of World I, including local variants were fielded by the three countries in conflict, Germany with the MG08 incaliber 7.92 ×57 mmMauser, from ‘England with Vickers .303 British, and Russia with Pulemyot M1910 in7.62 ×54 mmR.
The modern definition refers to a class of large-caliber machine guns (approximately .50 or 12.7 mm) initiated by John Moses Browning with the Browning M2, and designed for a greater range, penetration and destruction against vehicles, buildings, aircraft read and fortifications, compared to cartridge rifle used in the medium machine guns (MMG) or general-purpose machine gun (GPMG). In this sense the term “heavy” refers to greater power and range compared to small or medium caliber weapons. This class saw extensive use during the
The German , although very effective against infantry, could not match the ability of the M2 anti-vehicle, a lack of which was noted and deplored by the Germans after the D-day.
The need for a weapon of great range and with anti-vehicle to bridge the gap between weapons only against infantry and weapons only against vehicles, has led to the great popularity of this class of weapons, and its constant modernization. Today, the M2 is a weapon in service for more time in ‘U.S.military, and most of the nations is equipped with some type of HMG.
According to the nomenclature modern machine guns with a caliber smaller than12 mmare considered medium machine guns, and guns with a caliber greater than20 mmare generally considered automatic cannon, no heavy machine guns.