A machine gun (MG) is a fully automatic and rifled firearm designed for sustained direct fire. Automatic firearms of caliber or more are usually classified as autocannons rather than machine guns.
As a class of military kinetic projectile weapons, machine guns are designed to be mainly used as infantry support weapons and generally used when attached to a bipod or tripod, a fixed mount or a heavy weapons platform for stability against recoil. Many machine guns also use belt feeding and open bolt operation, features not normally found on other infantry firearms.
Modern overview
Unlike semi-automatic firearms, which require one trigger pull per round fired, a machine gun is designed to continue firing for as long as the trigger is held down. In a military context, the term is used to refer to relatively heavy crew-served weapons, able to provide continuous or frequent bursts of automatic fire for as long as ammunition can be fed. In non-military contexts, it is broadly used to refer to fully automatic weapons generally, regardless of caliber or form factor. While technical use of the term "machine gun" has varied, the modern definition used by the Sporting Arms and Ammunition Manufacturers' Institute of America is "a fully automatic firearm that loads, fires and ejects continuously when the trigger is held to the rear until the ammunition is exhausted or pressure on the trigger is released". This definition excludes most early manually operated repeating arms the Gatling gun and such as volley guns like the Nordenfelt gun.
Machine guns are used against infantry, low-flying aircraft, small boats and lightly/unarmored land vehicles, and can provide suppressive fire (either directly or indirectly) or enforce area denial over a sector of land with grazing fire. They are commonly mounted on fast attack vehicles such as technicals to provide heavy mobile firepower, armored vehicles such as tanks for engaging targets too small to justify the use of the primary weaponry or too fast to effectively engage with it, and on aircraft as defensive armament or for strafing ground targets, though on fighter aircraft true machine guns have mostly been supplanted by large-caliber rotary guns.
Although subdivided into "light", "medium", "heavy" or "general-purpose", even the lightest dedicated machine guns tend to be substantially larger and heavier than standard infantry arms. Heavy machine guns are either mounted on a tripod or on a vehicle; when carried on foot, the machine gun and associated equipment (tripod, ammunition, spare barrels) require additional crew members.
The term heavy machine gun originated in World War I to describe heavyweight medium machine guns, and persisted into World War II with Japanese Hotchkiss M1914 clones; today, however, it is used to refer to automatic weapons with a caliber of at least , but less than .
Many heavy machine guns, such as the Browning M2 .50 BMG machine gun, are accurate enough to engage targets at great distances. During the Vietnam War, Carlos Hathcock set the record for a long-distance shot at with a .50 caliber heavy machine gun he had equipped with a telescopic sight.Henderson, Charles (2005). Marine Sniper. Berkley Caliber. . This led to the introduction of .50 caliber anti-materiel sniper rifles, such as the Barrett M82.
History
The first successful machine-gun designs were developed in the mid-19th century. The key characteristic of modern machine guns, their relatively high rate of fire and more importantly mechanical loading, first appeared in the Model 1862 Gatling gun, which was adopted by the United States Navy. These weapons were still powered by hand; however, this changed with Hiram Maxim's idea of harnessing recoil energy to power reloading in his Maxim machine gun. Dr. Gatling also experimented with electric-motor-powered models; as discussed above, this externally powered machine reloading has seen use in modern weapons as well.
Medieval
The first known ancestors of multi-shot weapons were medieval organ guns. An early example of an attempt at the mechanisation of one of these would be an 'engine of war' produced in the mid-1570s in England capable of firing from 160 to 320 shots 4, 8, 12 or 24 bullets at a time at a rate of fire up to roughly 3 times the rate of fire of the typical arquebusier of the day. It was also claimed that the gun could be reloaded 'as often as you like' and fired no matter the weather though the English government never adopted the weapon despite testing being carried out at the Tower of London. The first firearms to have the ability to fire multiple shots from a single barrel without a full manual reload were revolvers made in Europe in the late 1500s. One is a shoulder-gun-length weapon made in Nuremberg, Germany, circa 1580. Another is a revolving arquebus, produced by Hans Stopler of Nuremberg in 1597.
17th century True repeating long arms were difficult to manufacture prior to the development of the unitary firearm cartridge; nevertheless, lever-action repeating rifles such as the Kalthoff repeater and Cookson repeater were made in small quantities in the 17th century.
Perhaps the earliest examples of predecessors to the modern machine gun are to be found in East Asia. According to the Wu-Pei-Chih, a booklet examining Chinese military equipment produced during the first quarter of the 17th century, the Chinese army had in its arsenal the 'Po-Tzu Lien-Chu-P'ao' or 'string-of-100-bullets cannon'. This was a repeating cannon fed by a hopper containing balls which fired its charges sequentially. The way it worked was similar to the Perkins steam gun of 1824 or the Beningfield electrolysis gun of 1845 only slow-burning gunpowder was used as the propelling force in place of steam or the gases produced by electrolysis. Another repeating gun was produced by a Chinese commoner, Dai Zi, in the late 17th century. This weapon was also hopper-fed and never went into mass production.
In 1655, a way of loading, aiming and shooting up to 6 wall muskets 60 times in a minute for a total rate of fire of 360 shots per minute was mentioned in The Century of Inventions by Edward Somerset, 2nd Marquess of Worcester, though, like all the inventions mentioned in the book, it is uncertain if it was ever built.
It is sometimes claimed (i.e. in George Morgan Chinn's the Machine Gun) that in 1663 the first mention of the automatic principle of machine guns was in a paper presented to the Royal Society of England by Palmer, an Englishman who described a volley gun capable of being operated by either recoil or gas. However, no one has been able to find this paper in recent times and all references to a multi-shot weapon by a Palmer during this period appear to be referring to a somewhat more common Kalthoff repeater or Lorenzoni-system gun. Despite this, there is a reference in 1663 to at least the concept of a genuine automatic gun that was presented to Prince Rupert, though its type and method of operation are unknown.
18th century
The 18th century saw a continuing stream of multi-shot and rapid-fire ordnance proposals across France, England, and the German states, most of them crank- or hand-operated cannon firing at rates that, however exaggerated in the reporting, far outpaced the conventional artillery of the day. In 1708 it was reported from Constantinople that a French officer had invented a very light single-barreled cannon capable of firing 30 shots in two and a half minutes, a rate of 12 a minute, and in 1711 a French lawyer named Barbuot presented to the parliament of Dijon a crank-operated "war machine" of ten carbine barrels loaded from a "drum" and firing in volleys. It was claimed to be accurate at 400 to 500 paces, to strike with enough force to pierce two or three men at close range, to fire five or six times before infantry came within musket range or cavalry within pistol range, and to be nearly as manoeuvrable as cavalry; a heavier version was said to throw grenades, and it was proposed to fit the machine with a bellows for clearing the smoke of firing.
The best-documented design of the era was that of James Puckle, a London lawyer who patented "The Puckle Gun" on 15 May 1718. A manually operated 1.25 in. (32 mm) caliber flintlock cannon with a revolver cylinder firing six to eleven rounds before the cylinder was swapped out, it was intended for shipboard use.Original patent claim reproduced in: Francis Bannerman Sons, Bannerman Military Goods Catalogue #28 (1954) p. 103 It was among the earliest weapons to be called a machine gun, being described as such in 1722, though its operation does not match the modern sense of the term; Puckle claimed it could fire round bullets at Christians and square bullets at Turks. It was nonetheless a commercial failure, never adopted or produced in meaningful quantity.
French and other Continental inventors remained especially active. Philippe Vayringe demonstrated a small cannon firing 16 shots in succession before the Duke of Lorraine in 1720, and a French report of 1729 described a machine able to fire 600 balls in a few minutes. In 1737 it was reported that Jacob de Weinholtz, a Dane serving in the Portuguese army, had invented a cannon firing 20 to 30 shots a minute but requiring fifteen men to work it; examples were taken with a Portuguese fleet sent to India for a colonial war in the 1740s. The same year a German engineer was said to have built a 10-pounder firing 20 times a minute, and in 1740 the Frenchman Chevalier de Benac developed a cannon firing 11 times a minute.
Britain and Denmark produced comparable designs around mid-century. In 1747 James Allis presented to the Royal Society a cannon said to charge and discharge itself 20 times a minute, and in 1750 a Prussian known as Captain Steuben of the Train of Artillery demonstrated to the King of Denmark a breech-loading cannon worked by four men, fed by paper cartridges, and firing 24 times a minute. In his satire, The Chinese Spy, Ange Goudar writes that the fictional Chinese mandarin Cham-pi-pi assisted in proofing a "great gun" capable of 60 shots a minute in Paris, 1764. In 1773 Thomas Desaguliers invented a cannon firing 23 or 24 times a minute that cleaned itself after every shot, and in 1775 two large cannons built by an unidentified matross at Woolwich were reported to have fired 59 shots in 59 and a half seconds.
The later decades brought a series of multi-barrel volley designs anticipating the mitrailleuse. Also in 1775, the Frenchman Du Perron invented a breech-loading volley gun worked by three or four men, its 24 barrels discharging ten times a minute for 240 shots,Nouveau Règlement pour la filature des soies, (no publisher name or imprint), p. 25 , 1775 and in 1776 an inventor from Westmoreland in England produced a gun said to charge and discharge itself 120 times a minute "by the motion of one hand only". In 1777 the Philadelphia gunsmith Joseph Belton offered the Continental Congress a "new improved gun" able to fire up to twenty shots in five seconds; rather than the complex lever-action mechanisms of older repeaters, it used a simpler system of superposed loads loaded with a single large paper cartridge. Congress asked Belton to modify 100 flintlock muskets to fire eight shots in this manner but rescinded the order when his price proved too high. Two years later, in 1779, the British inventor William Wilson Wright produced a machine of 21 musket barrels worked by three men that he claimed could fire three times faster than a single man could load and fire a musket.