A rotary cannon, rotary autocannon, rotary gun or Gatling cannon, is any large-caliber multiple-barreled automatic firearm that uses a Gatling-type rotating barrel assembly to deliver a sustained saturational direct fire at much greater rates of fire than single-barreled autocannons of the same caliber. The loading, firing and ejection functions are performed simultaneously in different barrels as the whole assembly rotates, and the rotation also permits the barrels some time to cool. Rotary cannons, external or self-driven are used in aircraft over reciprocating bolt autocannons which are more prone to jamming in high g environments. The rotating barrels on nearly all modern Gatling-type guns are powered by an external force such as an electric motor, although internally powered gas-operated versions have also been developed.
The cyclic multi-barrel design synchronizes the firing/reloading sequence. Each barrel fires a single cartridge when it reaches a certain position in the rotation, after which the spent casing is ejected at a different position and then a new round is loaded at another position. During the cycle, the barrel has more time to dissipate some heat away to the surrounding air.
Due to the usually cumbersome size and weight of rotary cannon, they are typically mounted on weapons platforms such as vehicles, aircraft, or ships, where they are often used in close-in weapon systems.
In 1852 a revolving barrel gun with a unique method of ignition was proposed by an Irish immigrant to America by the name of Delany. [1]
The Gatling gun was another gun to use rotating barrels. It was designed by the American inventor Dr. Richard J. Gatling in 1861 and patented in 1862. [2] Hand cranked and hopper fed, it could fire at a rate of 200 rounds per minute. The Gatling gun was a field weapon, first used in warfare during the American Civil War and subsequently by European and Russian armies.
The design was steadily improved; by 1876 the Gatling gun had a theoretical rate of fire of 1,200 rounds per minute, although 400 rounds per minute was more readily achievable in combat. By 1893, the M1893 Gatling gun could fire 800 to 900 rounds per minute. Gatling also developed examples of the M1893 powered by an electric motor driving the crank with a belt. [3] Tests demonstrated the electric Gatling could fire up to 1,500 rpm in bursts.
Ultimately, the Gatling's weight and cumbersome artillery carriage hindered its ability to keep up with infantry forces over difficult ground. It was eventually superseded by lighter and more mobile machine guns such as the Maxim gun. All models of Gatling guns were declared obsolete by the U.S. Army in 1911, after 45 years of service.
After the Gatling gun was replaced in service by newer non-rotating, recoil- or gas-operated machine guns, the approach of using multiple rotating barrels fell into disuse for many decades. Some examples were developed during the interwar years but only existed as prototypes or were rarely used. During World War I, Imperial Germany worked on the Fokker-Leimberger, an externally powered 12-barrel Gatling gun that could fire more than 7,200 7.92×57mm rounds per minute. [4]
After World War II, the U.S. Army Air Force determined that an automatic cannon of improved design with an extremely high rate of fire was required to achieve a sufficient number of large-caliber hits on fast-moving enemy jet aircraft. A larger-caliber cannon shell was deemed desirable as it could contain more explosives—compared to .30 and .50 caliber ammunition previously used—and thus able to destroy aircraft with only a few hits on target. However, autocannons suffered from a lower rate of fire than machine guns; a possible solution, the M39 revolver cannon, had problems with overheating and excessive barrel wear.
In June 1946, the General Electric Company was awarded a U.S. military defense contract to develop an aircraft gun with a high rate of fire which GE termed Project Vulcan. While researching prior work, ordnance engineers recalled the experimental electrically driven Gatling weapons of the turn of the 20th century. In 1946, a Model 1903 Gatling gun was borrowed from a museum and set up with an electric motor drive by General Electric engineers. During test firing, the 40-year-old design briefly managed a rate of fire of 5,000 rounds per minute.
In 1949 General Electric began testing the first model of its modified Gatling design, now called the Vulcan Gun. The first prototype was designated the T45 (Model A). It fired .60 in (15 mm) ammunition at about 2,500 rounds per minute from six barrels driven by an electric motor. In 1950, GE delivered ten initial model A T45 guns for evaluation. Thirty-three model C T45 guns were delivered in 1952 in three calibers: .60 cal., 20mm, and 27mm, for additional testing. After extensive testing, the T171 20mm gun was selected for further development. In 1956, the T171 20mm gun was standardized by the U.S. Army and U.S. Air Force as the M61 20mm Vulcan aircraft gun.
One of the main reasons for the resurgence of the electrically or hydraulically powered multiple-barrel design is the weapon's tolerance for continuously high rates of fire. For example, 1000 rounds per minute of continuous fire from a conventional single-barreled weapon ordinarily results in rapid barrel heating followed by stoppages caused by overheating. In contrast, a five-barreled rotary gun firing 1000 rounds per minute fires only 200 rounds per barrel per minute, an acceptable rate of fire for continuous use. A multiple-barrel design also overcomes the limiting factor of the loading and extraction sequence. In a single-barrel design, these tasks must alternate, limiting the rate of fire. A multiple-barrel design allows loading and extraction to occur simultaneously on different barrels as they rotate. The design is also resistant to defective ammunition, which can cause normal machine guns to malfunction when a cartridge fails to load, fire, or eject from the weapon. Since the power source of a multiple-barrel design is external, it can simply extract defective rounds as it would a regular, spent cartridge.
The M61 Vulcan 20 mm autocannon is the best-known of a family of weapons designed by General Electric and currently manufactured by General Dynamics. The M61 is a six-barreled 20mm rotary cannon that fires at up to 6,600 rounds per minute. [5] Similar systems are available in calibers ranging from 5.56 mm to 30 mm (the prototype T249 Vigilante AA platform featured a 37 mm chambering).
Another multi-barrel design is the hydraulically driven GAU-8 Avenger 30 mm autocannon, carried on the A-10 Thunderbolt II (Warthog) attack aircraft, a heavily armored close air-support aircraft. It is a seven-barreled cannon designed for tank-killing and is currently the largest bore multi-barrel weapon active in the U.S. arsenal, and heaviest autocannon ever mounted into an aircraft, outweighing the WW II German Bordkanone BK 7,5 75mm aircraft-mount, tank-killing single barrel autocannon by some 630 kg (1,389 lb), with ammunition.
The Gryazev-Shipunov GSh-6-23 and GSh-6-30 are Russian gas-powered rotary cannon with maximum cyclic rates of 9,000 to 10,000 rounds per minute.
While electric motors were used to rotate the Vulcan barrels, a few examples of self-operated Gatling-derived weapons use the blow-forward, recoil or gas impulse from their ammunition. The Bangerter machine gun uses a blow-forward operation and is the most complex example. The Slostin machine gun uses a similar operation but with gas pistons on each barrels. The GShG-7.62 machine gun and GSh-6-23, both use a more effective, simpler gas piston drive in the center of the barrel cluster.
The Minigun is a type of rotary machine gun. During the Vietnam War, the 7.62 mm caliber M134 Minigun was originally created to arm rotary-wing aircraft, and could be fitted to various helicopters as either a crew-served or a remotely operated weapon. It has a rate of fire from 2,000 to 6,000 rounds per minute [6] from a 4,000-round linked belt.
As the GAU-2B/A, the Minigun was also used on the U.S. Air Force AC-47, AC-119 and Lockheed AC-130 gunships. The AC-47 was known during the Vietnam War as "Puff the Magic Dragon" and was said to be "the only thing that scared the VC". This weapon was also used on selected USAF helicopters. With sophisticated navigation and target identification tools, Miniguns can be used effectively even against concealed targets. The crew's ability to concentrate the Minigun's fire very tightly produces the appearance of the 'Red Tornado' [7] from the light of the tracers, as the gun platform circles a target at night.
The Gatling gun is a rapid-firing multiple-barrel firearm invented in 1861 by Richard Jordan Gatling. It is an early machine gun and a forerunner of the modern electric motor-driven rotary cannon.
A machine gun (MG) is a fully automatic and rifled firearm designed for sustained direct fire with rifle cartridges. Other automatic firearms such as automatic shotguns and automatic rifles are typically designed more for firing short bursts rather than continuous firepower and are not considered true machine guns. Submachine guns fire handgun cartridges rather than rifle cartridges, therefore they are not considered machine guns, while automatic firearms of 20 mm (0.79 in) caliber or more are classified as autocannons rather than machine guns.
The M61 Vulcan is a hydraulically, electrically, or pneumatically driven, six-barrel, air-cooled, electrically fired Gatling-style rotary cannon which fires 20 mm × 102 mm rounds at an extremely high rate. The M61 and its derivatives have been the principal cannon armament of United States military fixed-wing aircraft for over sixty years.
An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bullets) fired by a machine gun. Autocannons have a longer effective range and greater terminal performance than machine guns, due to the use of larger/heavier munitions, but are usually smaller than tank guns, howitzers, field guns, or other artillery. When used on its own, the word "autocannon" typically indicates a non-rotary weapon with a single barrel. When multiple rotating barrels are involved, such a weapon is referred to as a "rotary autocannon" or occasionally "rotary cannon", for short.
The M197 electric cannon is a 20 mm three-barreled electric Gatling-type rotary cannon used by the United States military.
The General Dynamics GAU-12/U Equalizer is a five-barrel 25 mm Gatling-type rotary cannon. The GAU-12/U is used by the United States, Italy and Spain, which mount the weapon in their attack jets such as the AV-8B Harrier II, airborne gunships such as the Lockheed AC-130, and land-based fighting vehicles. A lighter four-barrel version, designated GAU-22/A, is mounted on F-35 Lightning II fighter jets.
A revolver cannon is a type of autocannon, commonly used as an aircraft gun. It uses a cylinder with multiple chambers, similar to those of a revolver handgun, to speed up the loading-firing-ejection cycle. Some examples are also power-driven, to further speed the loading process. Unlike a rotary cannon, a revolver cannon only has a single barrel, so its spun weight is lower. Automatic revolver cannons have been produced by many different manufacturers.
The M134 Minigun is an American 7.62×51mm NATO six-barrel rotary machine gun with a high rate of fire. It features a Gatling-style rotating barrel assembly with an external power source, normally an electric motor. The "Mini" in the name is in comparison to larger-caliber designs that use a rotary barrel design, such as General Electric's earlier 20 mm M61 Vulcan, and "gun" for the use of rifle ammunition as opposed to autocannon shells.
The Gryazev-Shipunov GSh-6-23 is a six-barreled 23 mm rotary cannon used by some modern Soviet/Russian military aircraft.
The Gryazev-Shipunov GSh-23 is a twin-barreled 23 mm autocannon developed in the Soviet Union, primarily for military aircraft use. It entered service in 1965, replacing the earlier Nudelman-Rikhter NR-23 and Rikhter R-23.
Rate of fire is the frequency at which a specific weapon can fire or launch its projectiles. This can be influenced by several factors, including operator training level, mechanical limitations, ammunition availability, and weapon condition. In modern weaponry, it is usually measured in rounds per minute or rounds per second.
The XM214 Microgun is an American prototype 5.56 mm rotary-barreled machine gun. It was designed and built by General Electric. The XM214 was a scaled-down smaller and lighter version of the M134 Minigun, firing M193 5.56×45mm ammunition.
The Gast gun was a German twin barrelled machine gun that was developed by Karl Gast of Vorwerk und Companie of Barmen and used during the First World War. Its unique operating system produced a very high rate of fire of 1,600 rounds per minute. The same principle was later used as the basis for the widely used Gryazev-Shipunov GSh-23L series of Russian aircraft autocannon.
The GAU-19/A is an electrically driven, three-barrel rotary heavy machine gun that fires the .50 BMG cartridge.
The Glagolev-Shipunov-GryazevGShG-7.62 is a four-barreled rotary machine gun designed in the Soviet Union, similar to firearms such as the M134 Minigun. It is a hybrid weapon using both propellant gas and an electric drive to rotate the barrels, which is in contrast with most other rotary guns. It was developed in 1968–1970 for the Mi-24 helicopter together with YakB 12.7mm machine gun, and is currently used in GUV-8700 gun pods, and flexible mounts on Kamov Ka-29.
The T249 Vigilante was a prototype 37 mm self-propelled anti-aircraft gun (SPAAG) designed as a replacement for the Bofors 40 mm gun in both towed and self-propelled forms in US Army service. The system consisted of a 37 mm T250 six-barrel rotary cannon mounted on a modified M113 armored personnel carrier chassis.
A multiple-barrel firearm is any type of firearm with more than one gun barrel, usually to increase the rate of fire or hit probability and to reduce barrel erosion or overheating.
The Fokker-Leimberger was an externally powered, 12-barrel rifle-caliber rotary gun developed in Germany during the First World War. The action of the Fokker-Leimberger differed from that of a Gatling in that it employed a rotary split-breech design, also known as a "nutcracker".
The XM301 Cannon was an externally powered, three-barrel 20 mm rotary cannon made by General Dynamics for the United States Army. Developed for use with the RAH-66 Comanche stealth helicopter, it is the world's lightest 20 mm rotary cannon. The XM301 was designed to be a versatile and accurate lightweight cannon that could serve both an air-to-air and air-to-ground role. Development and manufacture of the XM301 was cancelled in 2004 along with its parent RAH-66 program.
A repeating firearm or repeater is any firearm that is capable of being fired repeatedly before having to be manually reloaded with new ammunition from the magazine.