The Model 1873 Trapdoor Springfield was the first standard-issued breech-loading rifle adopted by the United States Army (although the Model 1866 trapdoor had seen limited issue to troops along the Bozeman Trail in 1867). The gun, in both full-length and carbine versions, was widely used in the Black Hills War and in subsequent battles against the American Indians.
The Model 1873 was the fifth variation of the Allin trapdoor design, and was named for its hinged breechblock, which opened like a trapdoor. The infantry rifle model featured a 32⅝-inch (829 mm) barrel, while the cavalry carbine used a 22-inch (560 mm) barrel.
The rifle cartridge was designated as „.45-70-405″, indicating a .45 caliber, 405-grain (26.2 g) bullet propelled by 70 grains (4.5 g) of black powder. It had a muzzle velocity of 1,350 feet per second (410 m/s), making it a powerful and effective load for the skirmish tactics of the era. A reduced-power load of 55 grains (3.6 g) of powder (.45-55-405) was manufactured for use in the carbine to lighten recoil for mounted cavalry soldiers. This cartridge had a correspondingly reduced muzzle velocity of 1,100 feet per second (340 m/s) and a somewhat reduced effective range.
The rifle was originally issued with a copper cartridge and used in the American West during the second half of the 1800s, but the soldiers soon discovered that the copper expanded excessively in the breech when heated after firing. This sometimes jammed the rifle by preventing extraction of the fired cartridge case. A jam required manual extraction with a knife blade or similar tool, and could render the carbine version of the weapon, which had no ramrod to remove stuck cases, useless in combat except as a club.
After the annihilation of General George Armstrong Custer’s battalion (armed with the carbine and .45-55 ammunition) at the Battle of Little Big Horn in June 1876, investigations revealed that jamming of their carbines may have played a factor. The cartridge was subsequently redesigned with a brass case, since that material did not expand as much as copper. This proved to be a major improvement, and brass became the primary material used in United States military cartridges from then to the present.
After the Little Big Horn disaster, troops were required to perform target practice twice a week; some became so proficient that they began winning the Army’s newly created marksmanship awards.