The Gallager carbine is an American black powder breechloading rifle produced in the American Civil War.
The weapon was designed by Mahlon J. Gallager, who licensed the design to Richardson and Overman of Philadelphia for production. On 31 August 1861 the first weapons were sold to the Army.
The Gallager was loaded from the rear with brass cases, which contained the projectile and the propellant. Covered by a disc made of greased felt, the projectile was inserted in the barrel after it was tilted up by a lever, followed by the case, and (like the concurrent muzzleloaders, such as the Springfield) were ignited by percussion cap, which was placed on the bolt face. The brass cases had a paper patch in the base, to prevent powder seepage and still allow the cap to fire the round. The weapon was 0.525 in (13.3 mm) caliber with a 22 in (56 cm) barrel.
The rifle was strongly made, but unpopular with troops. Frequently, the cases stuck due to expansion of the front part and had to be laboriously removed.
A total of 17,782 were sold to the U.S. Army.