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The M2 Machine Gun or Browning .50 Caliber Machine Gun is a heavy machine gun designed towards the end of World War I by John Browning. Its design is similar to Browning's earlier M1919 Browning machine gun, which was chambered for the .30-06 cartridge. The M2 uses the much larger and much more powerful .50 BMG cartridge, which was developed alongside and takes its name from the gun itself (BMG standing for ''Browning Machine Gun''). It has been referred to as "Ma Deuce", in reference to its M2 nomenclature. The design has had many specific designations; the official designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly armored vehicles and boats, light fortifications and low-flying aircraft. The M2 machine gun has been produced longer than any other machine gun. The Browning .50 caliber machine gun has been used extensively as a vehicle weapon and for aircraft armament by the United States from the 1930s to the present. It was heavily used during World War II, the Korean War, the Vietnam War, the Falklands War, the Iraq War and the War in Afghanistan in the 2000s and 2010s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries. The M2 has been in use longer than any other small arm in U.S. inventory except the .45 ACP M1911 pistol, also designed by John Browning. The current M2HB is manufactured in the United States by General Dynamics and U.S. Ordnance for use by the United States government, and for U.S. Foreign Allies via FMS sales. ==History== Machine guns were heavily used in World War I, and weapons of larger than rifle caliber were appearing. Both the British and French had large caliber machine guns. The larger rounds were needed to defeat the armor that was being introduced to the battlefield. Armor was also appearing in the skies. During World War I, the Germans introduced a heavily armored airplane, the Junkers J.I. The armor made aircraft machine guns using conventional rifle ammunition (such as the .30-06) ineffective.〔, stating "The Germans put a heavily armored plane into service during the closing days of World War I. This act made obsolete for all time the rifle-caliber machine gun for aerial use. Some countries were slower to accept the fact than others but nevertheless it cannot be disputed. The United States was among the first to come to this realization."〕 Consequently, the American Expeditionary Force's commander General John J. Pershing asked for a larger caliber machine gun. Pershing asked the Army Ordnance Department to develop a machine gun with a caliber of at least and a muzzle velocity of at least .〔 U.S. Col. John Henry Parker, commanding a machine gun school in France, observed the effectiveness of a French incendiary armor-piercing round. The Army Ordnance Department ordered eight experimental Colt machine guns rechambered for the French 11-mm cartridge. The French had developed a prototype machine gun for an even larger caliber. The French 11-mm round was found to be unsuitable because its velocity was too low. Pershing wanted a bullet of at least and a muzzle velocity of . Development with the French round was dropped.〔 Around July 1917, John M. Browning started redesigning his .30 caliber machine gun for a larger caliber. Winchester worked on the cartridge, which was a scaled up version of the .30-06. Winchester initially added a rim to the cartridge because the company wanted to use the cartridge in an anti-tank rifle, but Pershing insisted the cartridge be rimless.〔 The first .50 machine gun underwent trials on 15 October 1918. It fired at less than 500 rounds per minute, and the muzzle velocity was only . Cartridge improvements were promised. The gun was heavy, difficult to control, fired too slowly for anti-personnel, and was not powerful enough against armor. While the .50 was being developed, some German anti-tank rifles and ammunition were seized. The German rounds had a muzzle velocity of , an bullet, and could pierce at .〔. Chinn states that the German round was 12.7-mm anti-tank, but it may have been the 13.2mm TuF round. The Germans were working on their MG 18 TuF heavy machine gun.〕 Winchester made the .50 caliber round have similar performance. Ultimately, the muzzle velocity was . Efforts by John M. Browning and Fred T. Moore resulted in the water-cooled Browning machine gun, caliber .50, M1921. An aircraft version was termed the Browning aircraft machine gun, caliber .50, M1921. These guns were used experimentally from 1921 until 1937. They had light-weight barrels and the ammunition only fed from the left side. Service trials raised doubts whether the guns would be suitable for aircraft or for anti-aircraft use. A heavy barrel M1921 was considered for ground vehicles. John M. Browning died in 1926. Between 1927 and 1932, Dr. S.H. Green studied the design problems of the M1921 and the needs of the armed services. The result was a single receiver design that could be turned into seven types of .50 caliber machine guns by using different jackets, barrels, and other components. The new receiver allowed right or left hand feed. In 1933, Colt manufactured several prototype Browning machine guns (including what would be known as the M1921A1 and M1921E2). With support from the Navy, Colt started manufacturing the M2 in 1933. FN Herstal (Fabrique Nationale) has manufactured the M2 machine gun since the 1930s. General Dynamics, U.S. Ordnance, and Manroy Engineering (UK) are other current manufacturers. A variant without a water jacket, but with a thicker-walled, air-cooled barrel was designated the M2 HB (''HB'' for ''Heavy Barrel''). The added mass and surface area of the heavy barrel compensated somewhat for the loss of water-cooling, while reducing bulk and weight: the M2 weighs with a water jacket, but the M2 HB weighs . Due to the long procedure for changing the barrel, an improved system was developed called QCB (quick change barrel). The lightweight ''"Army/Navy"'' prefixed AN/M2 "light-barrel" version of the Browning M2 weighing was also developed, and became the standard .50-caliber aviation machine gun of the World War II-era for American military aircraft of nearly every type, readily replacing Browning's own air-cooled .30 caliber machine gun design in nearly all American aircraft installations. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「M2 Browning」の詳細全文を読む スポンサード リンク
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