The .70-150 Winchester was a hypothetical centerfire rifle cartridge of American origin.
Designed sometime around 1888, the .70-150 Winchester appeared on Winchester's cartridge boards as mock-up dummy rounds. It had never made it past the proposal/experimental stage.
Allegedly, only one known weapon was made for this caliber; a variant of the Winchester Model 1887 shotgun that featured a barrel with rifling at the last six inches forward of its bore. A small number of these weapons were manufactured and had never entered commercial production.
According to some sources, one of these modified Model 1887s was made specifically for Paul Foster.
The .70-150 Winchester is a large-bore rifle cartridge. It is based on a brass 12 gauge (some sources claim 10 gauge) casing that is necked down to accept a .73 inch bullet.
The casing has a capacity for 150 grains of propellant. The projectile weighs between 700 and 900 grains (43.5 and 58.3 grams).
Theoretically, the cartridge could achieve a muzzle velocity of 1,300 to 1,500 feet per second (396.24 to 457.2 meters per second) with a muzzle energy of nearly 3,800 ft-lbf (5,152.108 J).