Modern Gatling-style guns

After Gatling guns were replaced by lighter, cheaper blowback-style weapons, the approach of using multiple rotating barrels fell into disuse for many decades. However, Gatling gun-style weapons made a return in the 1940–50s, when weapons with very high rates of fire were needed in military aircraft. For these modern weapons, electric motors are used to rotate the barrel, although systems that derive power from their ammunition do exist such as the GSh-6-23, which uses a gas-operated drive system.

One of the main reasons for the resurgence of the Gatling gun-style design is the weapon's tolerance for continuous high rates of fire. For example, if 500 rounds were fired at a high rate from a conventional single-barrel weapon, this would likely result in the barrel overheating (distorting in extreme cases) or a weapon jam. In contrast, a five-barreled Gatling gun-style weapon firing 500 rounds, only fires 100 rounds per barrel, an acceptable rate of fire. Ultimately the limiting factor is the rate at which loading and extraction can occur. In a single barrel design these tasks must alternate, a multiple barrel design on the other hand lets them occur simultaneously, with different barrels at different points in the cycle. Their high rate of fire also makes them useful in systems that have little time to engage their targets, such as CIWS which defend against fast-moving anti-ship missiles.

The M61 Vulcan 20 mm cannon is the most prolific member of a family of weapons designed by General Electric and currently manufactured by General Dynamics. It is a six-barreled rotary cannon capable of more than 6,000 rounds per minute. Similar systems are available ranging from 5.56 mm to 30 mm (there was even a 37 mm Gatling on the prototype T249 Vigilante AA platform); the rate-of-fire being somewhat inversely-proportional to the size and mass of the ammunition (which also determines the size and mass of the barrels).

Another Gatling design well-known among aviation enthusiasts is the GAU-8 Avenger 30 mm cannon, carried on the A-10 Thunderbolt II (Warthog) attack aircraft. It is a seven-barreled cannon designed for tank-killing and is currently the largest bore Gatling weapon active in the U.S. arsenal.

During the Vietnam War, the 7.62 mm caliber M134 Minigun was created as a helicopter weapon. Able to fire 6,000 rounds per minute from a 4,000-round linked belt, the Minigun proved to be one of the most effective non-explosive projectile weapons ever built and is still used in helicopters today.

They are also used on USAF AC-47, AC-119 and Lockheed AC-130 gunships, their original high-capacity cargo airframes able to house the items needed for sustained operation. With sophisticated navigation and target identification tools, Miniguns can be used effectively even against concealed targets. The crew's ability to concentrate the Gatling's fire very tightly produces the appearance of the 'Red Tornado' from the light of the tracers, as the gun platform circles a target at night.

The GAU-8 Gatling gun of an A-10 Thunderbolt II at Osan Air Base, Korea.

The Minigun features in several action movies including Terminator 2 and Predator, but in reality they are unusable as unmounted personal weapons, the high rate of fire (with accompanying recoil), mechanical and power-supply complexity and heavy weight making them impractical compared to a light machine gun.

Gatling Gun

A Gatling gun is a gun with multiple firing pins and breeches connected to multiple rotating barrels. Each barrel fires a single shot as it reaches a certain point in the cycle after which it ejects the spent cartridge, loads a new round, and in the process, somewhat cools down. This configuration allows higher rates of fire without the problem of an overheating single barrel, though accuracy suffers. The gun was designed by the American inventor Dr. Richard J. Gatling in 1861 and patented in 1862.

Although it was not an automatic firearm, the Gatling gun is considered by some to have been the first machine gun. While the Gatling gun did not automatically reload under its own power, it was capable of firing continuously. The first Gatling gun relied on a hand crank for external power. The Maxim gun, invented in 1884, was the first self-powered machine gun. Some time later, Gatling-type weapons were invented that diverted a fraction of gas from the chamber to spin the rotating barrels. Later still, electric motors supplied external power.

Mitrailleuse

The mitrailleuse was a manually-fired volley gun originally developed in Belgium in the 1850s by Fafschamps and improved during the early 1860s by Christophe and Montigny. The French-designed Reffye mitrailleuse followed soon afterwards and was adopted by the French Army in 1865, with the personal support of Napoleon III. Initially kept under wraps as a secret weapon, it became widely used in battle by French artillery during the Franco-Prussian War (1870-1871). Smaller numbers of other designs, including the Gatling gun, were also purchased by the French government during the latter part of that conflict. The Reffye mitrailleuse had initially been built in small numbers and in secrecy: only about 200 were available for field deployment in July 1870 at the beginning of the conflict. Historically, however, it was the first rapid-firing weapon to be deployed as standard equipment by any army in a major conflict. Although innovative, it failed as a tactical weapon because its operational usage and design were flawed. The word mitrailleuse nonetheless became the generic term for a machine gun in the French language, although the mitrailleuse itself was entirely manually-operated.

Machine gun

A machine gun is a fully-automatic mounted or portable firearm, usually designed to fire rifle cartridges in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute. The first machine guns were manually operated, for example, by turning a hand crank.

In United States law, machine gun is a term of art for any fully-automatic firearm, and also for any component or part that will modify an existing firearm into a fully-automatic firearm.

Operating principles

There have been two main machine gun eras: the era of manual machine guns and the era of mason machine guns. The technical development itself is marked by a series of developments of specific automatic features, as well as technical developments (such as linked ammunition). The era of manual multi-shot devices extends back hundreds of years (such as manual volley guns), but the development of manual and automatic machine guns takes place almost entirely in the latter half of the 1800s. Manual machine guns are manually-powered, e.g., a crank must be turned to power reloading and firing, as opposed to simply holding down a trigger, as with automatic machine guns. There are many other notable features, but this is one of the most significant to allowing higher rates of fire common to machine guns.

Manual machine guns, as well as manual volley guns, saw their first major use in the American Civil War. The Gatling gun and "coffee gun" both used manually-powered automatic loading, fed via a hopper filled with cartridges. The Gatling gun would be the major type of the late 19th century, though there were many other manual designs with varying degrees of use (e.g. the Nordenfelt gun). The first automatic machine gun was the recoil-operated Maxim gun, which used linked (belt) ammunition, as well as a single barrel and automatic loading. This concept of using bullet energy would also drive the development of nearly all other semi and fully automatic firearms of 20th century.

The two major operation systems of modern automatic machine guns are gas operation and recoil operation. As the name implies, the gas operated system uses the gas generated from the burning powder to cycle the action, whereas the recoil operated uses the recoil generated from the ejecting bullet. The first gas-operated machine gun was the Colt-Browning M1895.. It was followed shortly thereafter, in 1897, by the gas-operated Hotchkiss machine gun.

Another (minor) type is the externally-powered machine gun. Rather than human manual power or energy generated by the cartridge, an external source such as an electric motor is used. These types are now called by more specific names such as Minigun and Chain gun. They are common on fighting aircraft and ground vehicles, where the externally powered mechanism allows for automatic clearing of many failure conditions that would otherwise disable the firearm.

General purpose machine gun

A general purpose machine gun (GPMG) in concept is a multi-purpose weapon, a machine gun intended to fill the role of either a light machine gun or medium machine gun, while at the same time being man-portable. However, performance in either role may be inferior to a weapon specifically designed for that role. In modern practice, they are air-cooled medium machine guns firing rifle cartridges such as the 7.62x51mm NATO. They are generally operated from a stationary prone position from either a bipod or tripod, or mounted on a vehicle, as they are usually too powerful and heavy to be fired effectively on foot from an unsupported standing position or on the move.

The term GPMG (or "Jimpy" in British Army slang), which comes from the Belgian-French name Mitrailleuse d'Appui General or General Purpose Machineguns (GPMG), became popular for describing medium machine guns used in multiple roles. The original Belgian-French term Mitrailleuse a Gaz is also known to be used. The mediums fired rifle caliber ammunition, but had some concessions for more extended firing and more general usage. This generally included both bipod and tripod/pintle mounting options and quick-change barrels. The first medium machine gun used as a GPMG traces back to World War I, where aircooled medium machine guns were used in many different roles, typically with larger magazines on aircraft, tanks, and ships, and in lighter configurations by infantry on bipods or tripods.

During the inter-war period, Germany developed the Maschinengewehr 34, or MG34, from scratch as a GPMG, as opposed to an adaptation of an existing weapon, such as the MG08/15. The MG34 was air-cooled, belt-fed and had the ability to be mounted on a variety of fixtures and employed in several different roles. Notably, the MG34 remained the standard co-axial weapon for Nazi German vehicles through the Second World War. The MG34 was successful enough during use in the opening stages of the Second World War that the concept of the GPMG was adopted in many other post-WWII armies. The MG 34's immediate successor in Wehrmacht service, the MG42, was the most versatile and effective machine gun design of the Second World War. The MG3, a direct descendant of the MG42, is still in service with the German Army and others.

Belgian-made FN MAG.

The Belgian FN MAG, FN Mitrailleuse d'Appui General (general purpose machine gun) has long been the most widely-used GPMG among NATO and other western armies. The British Army and other Commonwealth forces used it to replace the venerable Vickers Gun, beginning in the late 1950s. It is known as the "Gympy"(Sometimes spelt "Jimpy") in British Army slang.

M240G general purpose machine gun.

The US Army has adopted the FN MAG as the M240 to replace the previous US GPMG (also widely used by allied nations), the M60 machine gun. The US Army uses the M249 - the MINIMI - as its light machine gun/squad automatic weapon, and the M2 machine gun (using the .50 BMG cartridge) is used in the heavy machine gun role.

In the late 1956, the Canadian Military adopted the FN MAG as the C6A1 GPMG along with the purchase of the FNC1 and FNC2's. Even though the C1's and the C2's have been replaced by the C7A1/ C7A2 rifle and the C9A1/ C9A2 LMG, the C6 is still used as a GPMG and is held in such high regard in the Canadian Army that 2 are deployed in each Platoon's Weapon detachment. Due to the need of a Heavy machine gun, the Browning .50 Cal has been brought back into service with the Canadian Army.

Since the late 1950s or early 1960s, the Czechs produced the vz. 59 general purpose machine-gun in both 7.62x54mmR and 7.62 mm NATO (for export models), for which light and heavy barrels were made for differing tactical roles. The approximate Russian equivalent is the PK/PKM family of multi-purpose machine-guns which has been in Russian, and previously Soviet, military service since 1964, and which has been widely exported.

Since 1967, the People's Republic of China has also produced a general purpose machine-gun in 7.62x54mmR as a hybrid weapon derived from several different machine-gun models and with the original model designation of Type 67; since then, second and third modified and improved models of this gun have been made and have been designated Type 67-1 and Type 67-2 respectively.

Heavy machine gun

The M2 Browning machine gun with a tripod weighs 58 kg (128 lb).

Polish partisans firing a Ckm wz.30 (a Polish-made clone of the American Browning M1917) in 1944.

A heavy machine gun refers to either a larger-caliber, high-power machine gun or one of the smaller, medium-caliber (rifle caliber) machine guns meant for prolonged firing from heavy mounts, less mobile, or static positions (or some combination of the two). The latter meaning is generally thought of as an older meaning, and the former as a modern one, but both weapon types have histories extending back to the 1800s. Furthermore, heavier smaller-caliber weapons continue to be used up to the present.

A classic example of a rifle-caliber heavy machine gun would be a water-cooled Maxim machine gun that was belt fed, had a water jacket, was crew served, and mounted on tripod or wheeled mount. Other types used linkable strips (such as the Hotchkiss) or large magazines. A common example of a heavy-caliber machine gun would be the M2 Browning .50-caliber machine gun. Firearms with calibers larger than 13 to 15 mm are generally thought of as autocannons instead of heavy machine guns.

Light machine gun

The FN Minimi, one of the most popular modern 5.56 mm light machine guns among NATO countries

A light machine gun or LMG is a machine gun that is generally lighter than other machine guns of the same period, and is usually designed to be carried by an individual soldier, with or without an assistant. Modern light machine guns often fire smaller-caliber cartridges than medium machine guns, and are usually lighter and more compact. LMGs are often used as squad automatic weapons.

Usually, a light machine gun is intended to act as a support weapon, in that it can generate a greater volume of continuous automatic fire than the usual firearms carried by infantry soldiers, at the cost of greater weight and higher ammunition consumption.

It is possible to fire a light machine gun from the hip or on the move, but they are usually fired from a prone position, especially when using a bipod. Early light machine guns (especially those derived from automatic rifles, such as the M1918 Browning Automatic Rifle) were sometimes magazine-fed. Some LMG's, such as the Russian RPK, are modifications of existing assault rifle designs. Adaptations generally include a larger magazine, heavier barrel to resist overheating, more robust action to support sustained fire, and often a bipod. Modern light machine guns are designed to fire more rounds of a smaller caliber ammunition and as such tend to use a belt of ammunition; this allows them to fire for longer periods of time without the need to reload. Other modern light machine guns, such as the FN Minimi, are capable of firing from either an ammunition belt or a detachable box magazine.