The end of the Civil War marked the end of the percussion period and the introduction to the cartridge era.  Metallic and paper cartridges had been known in the preceding centuries, but, whereas before they had merely served as handy powder and ball containers facilitating the handling and the loading, now they had become a self-contained unit possessing all the elements required for discharge; i.e., the primer ignition system, as well as the propelling charge of powder and the projectile.  Though the breech-loading principle had been recognized at the end of the Civil War as a necessary modernization in the shoulder arms for issue to the services, the Ordnance Department was faced with the usual problem of curtailed funds consequent to the end of the war, as well as some hundreds of thousands of serviceable if obsolete muzzle-loading shoulder arms in storage.  Accordingly, the Ordnance Department decided to utilize the muzzle-loading arms in stock by conversion to a system designed by Erskine S. Allin, Master Armorer of the Springfield Armory.

     The breech-loading mechanism designed by Allin retained the stock, barrel, lock plate, and furniture of the Model 1861-1863 arms, and added a new breech fitted to the milled barrel.  The conversion system used a rising breech block hinged at the front, which when raised by unlatching a thumb piece, exposed the breech for loading the chamber with a short, caliber .58 rim-fire copper case cartridge.  The cartridge was fired by a firing pin seated in the breech, struck by the conventional side hammer.  The cartridge contained 60 grains of powder and a 500 grain bullet.  Extraction was by a rack operated extractor, sliding in a slot on the right of the chamber, a weak extracting system.  5,000 rifle muskets were directed to be altered to the Allin system in 1865. 

     Our specimen was converted from a Model 1861.  The lock plate to the rear of the lock is dated 1862.  In front of the lock “US” “SPRINGFIELD” in two lines and an eagle.  The bands are marked “U”.  The top of the butt plate is marked “US”.  The left side of the barrel is marked “A”.  The barrel tang is marked “2”.  The bayonet is marked “US”.