 After considerable testing, the prototype developed by Erskine S. Allin of the government-operated Springfield Armory was chosen for its simplicity and the fact that it could be produced by the modification of existing Springfield Model 1863 muskets.These modifications cost about $5 per rifle (around $73 adjusted for inflation), which was a significant savings at a time when new rifles cost about $20 each (around $292 adjusted for inflation).Patent No.