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The carbine was designed and patented by Ambrose Burnside, who resigned his commission in the U.S. Army to devote himself full time to working on the weapon. The carbine used a special brass cartridge, also invented by Burnside. Pressing the weapon's two trigger guards opened the breech block and allowed the user to insert a cartridge. When the trigger was pulled, the hammer struck a percussion cap and caused a spark; a hole in the base of the cartridge exposed the black powder to this spark. The unique, cone-shaped cartridge sealed the joint between the barrel and the breech. Most other breech-loading weapons of the day tended to leak hot gas when fired, but Burnside's design eliminated this problem.