The Gatling gun was hand-crank operated with six barrels revolving around a central shaft, although some models had as many as ten. 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. Turning the crank rotated the shaft. The carrier was grooved and the lock cylinder was drilled with holes corresponding to the barrels.
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. 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. 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 unnecessary.
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.