Despite the name this cartridge was invented by P.O. Ackley a prolific American wildcatter. Wildcat cartridges are ones that are not made to a standard adopted by any major manufacturer.

This particular cartridge could send a .22 caliber round 5,000 fps (1,524 m/s). The case it uses in this picture is that of a .378 Weatherby Magnum necked down to hold a .223 caliber bullet, but another design of the same name used .50 BMG cases.