The .50-70 Government cartridge was a black powder round adopted in 1866 for the Springfield Model 1866 Trapdoor Rifle.
.50-70 Government Wikipedia
The cartridge was developed after the unsatisfactory results of the .58 rimfire cartridge for the Springfield Model 1865 Trapdoor Rifle.
The .50-70 Government cartridge became the official cartridge of the US military until replaced by the .45-70 Government in 1873. The .50-70 cartridge had a pressure limit of 22,500 PSI.
The official designation of this cartridge at the time of introduction was "US Center-fire Metallic Cartridge", and the commercial designation .50-70-450, standing for :
Powder Charge 70 grains (4.5 g) black powder
Bullet Weight 450 grains (29 g)
Since this cartridge is no longer commercially produced, reloaders have experimented with a variety of bullet weights from 425 to 600 grains (39 g) in weight. There is evidence that a reduced load version of this cartridge was officially produced for use in Sharps carbines converted to metallic cartridge ammunition, as well as cadet rifles. This used a 430-grain (28 g) bullet and 45 grains (2.9 g) of powder.
Buffalo Bill Cody used a Springfield Model 1866 in caliber .50-70 while hunting buffalo to feed the track workers of the Kansas Pacific Railroad (later Union Pacific Eastern Division).