Springfield Model 1865 The Springfield Model 1865 was an early breech - loading rifle manufactured by U . S . Armory in Springfield , Massachusetts . It was a modification of the Springfield rifled musket Model 1861 . It was later replaced with the Model 1866 . Description . During the U . S . Civil War , the advantage of breech loading rifles became obvious . The rifled musket s used during the war had a rate of fire of 3 or 4 rounds per minute . Breech loading rifles increased the rate of fire to 8 to 10 rounds per minute with the additional advantage that they can be easily loaded from a prone rather than standing position , reducing the visible cross section of the rifleman and thus vulnerability to counter - fire . As the Civil War drew to a close , the U . S . Ordnance Department requested prototypes of breech loading weapons from arms manufacturers all over the world . 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 , which was a significant savings at a time when new rifles cost about $ 20 each . Patent No . 49 , 959 was issued to Erskine S . Allin on September 19 , 1865 , describing the design . Specifications . The conversion from musket to breechloader was done by milling open the breech section of the barrel and inserting a hinged breechblock fastened to the top of the barrel . A thumb - operated cam latch at the rear of the breechblock held it shut when in closed position . The rack - type system extractor was withdrawn automatically as the breechblock was opened and snapped back at the end of its stroke . The firing pin was housed within the breechblock . The hammer nose was flattened to accommodate the firing pin . The breech mechanism employed a hinged breechblock that rotated up and forward , resembling the movement of a trapdoor , to open the breech of the rifle and permit insertion of a cartridge . The hinged breech block caused these rifles to be named " Trapdoor Springfields " . Approximately five thousand civil war Model 1861 rifled muskets were converted at the Springfield Armory in 1866 . It soon became apparent that many of the small working parts in the breech system were not going to have a long service life , and the action was too complicated for normal service use . Therefore , before the Model 1865 production order was completed , a less complex rifle was already being tested . This caused the Model 1865 to be called the " First Allin " , and the following revised model , the Springfield Model 1866 , to be called the " Second Allin " . The Springfield model 1865 fired a rimfire . 58 - 60 - 500 cartridge ( . 58 inch bullet , of black powder ) , the caliber matching that of the civil war minie ball , which was originally used in these rifles . The Model 1865 quickly became obsolete , and most of them were sold in the 1870s to several American arms dealers . At the time , there was a large demand in the US , for shorter cadet style rifles . To satisfy this need , these dealers cut the barrels and stocks to make short rifles with 33 " and 36 " barrel lengths . Likewise , the stock wrists were often thinned for cadet use .