Gatling Gun - Basic Design

Basic Design

The Gatling gun was hand-crank operated with six barrels revolving around a central shaft, although some models had as many as ten. 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-filled barrels 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 fully developed and become available. 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 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 gun had a theoretical rate of fire of 1,200 rounds per minute, although 400 rounds per minute was more likely in combat.

Each barrel fires once per revolution at about the same position. 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 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 caliber 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 invention was patented in U. S. 110,338. As each magazine emptied, the drum was manually rotated to bring a new magazine into use until all 400 rounds had been fired.

By 1893, the Gatling was adapted to take the new .30 Army smokeless cartridge. The new M1893 guns featured six barrels, and were capable of a maximum (initial) rate of fire of 800-900 rounds per minute. Dr. Gatling later used examples of the M1893 powered by electric motor and belt to drive the crank. Tests demonstrated the electric Gatling could fire bursts of up to 1,500 rpm.

The M1893, with minor revisions, became the M1895, and 94 guns were produced for the U.S. Army by Colt. Four M1895 Gatlings under Lt. John H. Parker saw considerable combat during the Santiago campaign in Cuba in 1898. The M1895 was designed to accept only the Bruce feeder. All previous models were unpainted, but the M1895 was painted olive drab (O.D.) green, with some parts left blued.

The Model 1900 was very similar to the model 1895, but with only a few components finished in O.D. green. The U.S. Army purchased a quantity of M1900s. All Gatling Models 1895-1903 could be mounted on an armored field carriage.

In 1903, the Army converted their M1900 guns in .30 Army to fit the new .30-03 cartridge (standardized for the M1903 Springfield rifle) as the M1903. The later M1903-'06 was an M1903 converted to .30-06. This conversion was principally carried out at the Army's Springfield Armory arsenal repair shops.

All models of Gatling guns were declared obsolete by the U.S. Army in 1911, after 45 years of service.