The .50-90 Sharps rifle cartridge is a black-powder cartridge that was introduced by Sharps Rifle Manufacturing Company in 1872 as a buffalo (American bison) hunting round. Like other large black-powder rounds, it incorporates a heavy bullet and a large powder volume, leading to high muzzle energies. The standard factory loads, produced and sold by the Sharps Rifle Manufacturing Company and the Sharps Rifle Company were .50/100/425 (.50 caliber/100 grains black powder/425 grain grease grooved bullet) and .50/100/473 with a paper patched bullet. Factory loads manufactured by any of the Sharps companies were mostly hand-loaded which made them expensive to produce. This naturally invited competition. Winchester offered the cartridge loaded .50/90/473 with paper patched bullets which may be how the cartridge came to be commonly known as the .50-90. The .50-90 Sharps is similar to the .50-100 Sharps and .50-110 Sharps cartridges. All three use the same 2.5-inch (64 mm) case, the latter two being loaded with more grains of black powder. All rifles made for the .50-90 Sharps should be able to use the .50-110 and .50-100 cartridges due to the case dimensions being nearly identical.
Bullet diameter was typically 0.512 inches (13.0 mm) diameter. Bullets weighed from 335 to 700 grains (21.7 to 45.4 g). Historical loads using black powder have muzzle energy in the 1,630 to 1,985 foot-pounds force (2,210 to 2,691 J) range, while modern loads using smokeless powder give 2,561 to 2,989 foot-pounds force (3,472 to 4,053 J) of energy.
