Colt .45 single action army (saa) revolver
Many were sold in .44-40 Winchester to allow cross-compatibility with the Winchester '73 lever action rifle.
That gun took a shorter, slightly less potent version of the .45 LC, called the .45 Schofield, which would also fit in the Colt SAA.
Despite the lower pressure, the muzzle velocity of the Single Action Army is about the same as—or slightly higher than—many .45 ACP pistols, due to its long barrel length.
Which was replaced by the Colt M1892, then the US Army temporary used the Peacemaker for a short time.
By 1876 the Colt SAA was being offered in additional calibers for civilian and foreign military sales.
The Colt Single Action Army, commonly known as the Peacemaker, is a single action revolver.
It was designed for the US cavalry by Colt and adopted in 1873, and it was perhaps the most prolific pistol in the Wild West.