Hello, SAA Gunslinger. When the U.S. army adopted the Model P in 1873..it was chambered for the .45 Colt. (They didn,t have to call it a "Long Colt"..because there were no short ones yet!). Then a Major Schofield began working on the side with Smith & Wesson, & they came up with a new top-break single action revolver...S&W named it the Schofield. The army did extensive field tests, and although it was faster to eject & load on horseback than the Colt, the army finally decided it was too complicated and dropped it.
when the Gov. gets involved in something there is a big screwup...Some units decided to keep their S&W's. The army had by now supplies of both cartridges scatered in various posts around the west...The S&W round would chamber in the Colt, but not vice-versa...BIG BIG problem if in a firefight & you are sent wrong ammo! What to do? They dropped the .45 Colt ctg. & adopted the shorter less powerful round!