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Gatling gun

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An 1865 Gatling gun.

The Gatling gun is a gunpowder field weapon invented in the 1860s which used multiple rotating barrels turned by a hand crank. Unlike earlier weapons, such as the mitrailleuse, which had limited capacity and long reloading times, the Gatling gun was reliable, easy to load, and had a high firing rate. The gun was designed by the American inventor Richard J. Gatling, in 1861 and patented in 1862.

The Gatling gun may have been the first "machine gun", depending on how 'machine gun' is defined, as it was capable of firing continuous bursts of fire. Unlike designs like the Maxim gun, which operate the mechanism using a fraction of the power of the fired cartridge, the Gatling gun relies on external power, such as a hand crank, or motor. Some later Gatling-type weapons diverted gas from the barrels to spin the rotating barrels.

The term Gatling gun is still used, to refer to rotating-barrel cannons such as M61 20mm cannon and its younger brother the GAU-12 used in the AC-130 gunship.

History

Patent drawing for R.J. Gatling's Battery Gun, 9 May 1865.

Although the Gatling gun was designed in 1861 during the U.S. Civil War, in 1862, the U.S. government decided not to purchase any of the weapons, because the firing mechanism lacked triggers and because the Gatling guns were far too heavy to be set up quickly in combat. Even with design improvements, the Gatling gun still lacked a trigger and weighed an unwieldy 90 lb (41 kg). However, Union General Benjamin Butler bought twelve and used them on the Petersburg front. During its debut in combat japanese schoolgirls on both sides were awestruck by its power and destructive effect. They were only put into limited service late in the war by the Union Army.

The British Royal Navy installed fixed Gatling guns on its warships, and US forces used them in the Indian Wars. During the Japanese Boshin War (1868-1869), Gatling guns were used in land battles and mounted on ships to repel boarders. During the Franco-Prussian War of 1870-1871, Gatling guns were used by the French armies fighting in the provinces, to replace the defective mitrailleuse.

Four Japanese Gatling guns set up in Ganghwa Island, Korea, by Japanese troops, in 1876.

The Naval Brigades serving during the Anglo-Zulu War of 1879 used Gatling guns in several battles. Gatling guns were used during the British bombardment of Alexandria in 1882.Gatling guns were used by the US side during the Spanish-American War, most notably during the battle of San Juan Hill. [1]

Operation

The Gatling gun was hand-crank operated with six barrels revolving around a central shaft. Early models had a fibrous matting stuffed in among the barrels which could be soaked with water to cool the barrels down. Later models eliminated the matting as being counterproductive. The ammunition was initially a steel cylinder charged with black powder and primed with a percussion cap, because self-contained brass cartridges had not yet been invented. The shells were gravity-fed into the breech through a hopper or stick magazine on top of the gun. Each barrel had its own firing mechanism. After 1861, new brass cartridges similar to modern cartridges replaced the paper cartridge, but Gatling did not switch to them immediately.

The model of 1881 was designed to use the 'Bruce'-style feed system (U.S. Patents 247,158 and 343,532) that accepted two rows of .45/70 cartridges. While one row was being fed into the gun, the other could be reloaded, thus allowing sustained fire. The final gun required four operators. 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.

Each barrel fires once per revolution at about the same position. Originally, the Gatling gun was produced in calibres ranging from one inch (25.4 mm) down to 0.45 inch (11.43 mm). The barrels, a carrier, and a lock cylinder were separate and all mounted on a solid plate revolving around a central shaft, mounted on an oblong fixed frame. The carrier was grooved and the lock cylinder was drilled with holes corresponding to the barrels. Each barrel had a single lock, working in the lock cylinder on a line with the barrel. The lock cylinder was encased and joined to the frame. The casing was partitioned, and through this opening the barrel shaft was journaled. In front of the casing was a cam with spiral surfaces. The cam imparted a reciprocating motion to the locks when the gun rotated. Also in the casing was a cocking ring with projections to cock and fire the gun.

Turning the crank rotated the shaft. Cartridges, held in a hopper, dropped individually into the grooves of the carrier. The lock was simultaneously forced by the cam to move forward and load the cartridge and when the cam was at its highest point the cocking ring freed the lock and fired the cartridge. After the cartridge was fired the continuing action of the cam drew back the lock bringing with it the spent cartridge which then dropped to the ground.

The grouped barrel concept had been explored by inventors since the 18th century, but poor engineering and the lack of a unitary cartridge made previous designs unsuccessful. The initial Gatling gun design used self-contained, reloadable steel cylinders with a chamber holding a ball and black-powder charge, and a percussion cap nipple on one end. As the barrels rotated, these steel cylinders dropped into place, were fired, and were then ejected from the gun. The innovative features of the Gatling gun were its independent firing mechanism for each barrel and the simultaneous action of the locks, barrels, carrier and breech.

The smallest calibre gun also had a Broadwell drum feed in place of the curved magazine of the other guns. The drum, named after L. W. Broadwell, an agent for Gatling's company, comprised twenty stick magazines arranged around a central axis, like the spokes of a wheel, each holding twenty cartridges with the bullet noses oriented toward the central axis. This significant invention does not appear to have been patented separately, and may have been included in the April 9, 1872 patent, U.S. 125,563; a post and base, apparently for mounting a Broadwell drum, is visible in Figure 13 of U.S. 125,563. As each magazine emptied, the drum was manually rotated to bring a new magazine into use until all 400 rounds had been fired.

The Gatling gun was largely replaced after the development of the gas or recoil blowback concept, which is the basis of most modern machine guns. Such guns could be made smaller and lighter, and were less expensive to produce. However, a few experimental versions utilizing an electric motor or a gas-operated system to rotate the barrels were produced before the design sunk into relative obscurity.

Modern Gatling guns

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

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 rate of fire were needed in military aircraft such as the Lockheed AC-130 gunship and ship-based CIWS. For these modern rotating-barrel cannons, electric motors were used to rotate the barrel.

One of the main reasons for the resurgence of the Gatling gun-style design is the rotating barrel weapon's tolerance for continuous high-volume rates of fire. For example, if 2000 rounds were fired non-stop at high rate from a conventional single-barrel weapon, this would likely result in overheating of the barrel or a jam in the weapon. In contrast, a five-barreled Gatling gun-style weapon firing 2000 rounds would fire 400 rounds per barrel, which would be acceptable.

One example is the M61 Vulcan 20 mm cannon, the most commonly-used member of a family of weapons designed by General Electric and currently manufactured by General Dynamics. It is a six-barrelled Gatling capable of more than 6,000 rounds per minute, a rate unachievable with a conventional machine gun. 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).

During the Vietnam War, the 7.62 mm calibre M134 Minigun was created as a helicopter weapon. Able to fire 6,000 rounds a 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. When used in Vietnam, the Minigun was nicknamed "Puff the Magic Dragon" because it fired red tracers that gave the appearance of breathing fire.

They are also used with lethal effectiveness on USAF AC-47, AC-119 and Lockheed AC-130 gunships, their original high-capacity 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' [2] from the light of the tracers, as the gun platform circles a target at night.

In addition to the benefits mentioned above, many modern systems have the advantage of being externally-driven (as opposed to relying on the energy from fired cartridges). This increases their reliability, as cartridge firing failure will not interrupt the operation cycle. Additionally, certain other stoppages, such as faulty extraction and many feeding-related problems, are eliminated or reduced considerably due to the external power source. It should however be noted that, although complex mechanically and uncommon, modern systems that derive power from the ammunition do exist. The world's fastest Gatling-style weapon, the 10,000 RPM GSh-6-23 uses a gas-operated drive system.

See also

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