In approximately 1871 Springfield Armory converted 1,108 Burnside-Spencer carbines by fitting the actions with rifle length barrels chambered for .50 caliber ammunition with three groove rifling. The armory also refurbished the parts and added a nearly full length forearm with two barrel bands and a slotted cleaning rod. The left side of the stock, just behind the saddle ring base, is marked with the correct "ESA" cartouche and the other components have the standard Burnside and armory markings including matching serial numbers. It has a blade front sight, notch and folding ladder rear sight, the Stabler cut-off device, and is fitted with a socket bayonet.

Very fine as Springfield Armory refurbished. 97% of the armory blue finish and case colors remain aside from some rub wear at the muzzle from the bayonet. The wood is also very fine and has strong, arsenal oil finish and a few minor scrapes and tooling marks. The action functions very well and the markings are crisp, however, the Stabler cut-off is loose and sometimes interrupts the falling breech block. The bayonet is very good with mild wear.