One of several high-velocity, rimless cartridges designed by Charles Newton for his bolt-action rifles, the 256 Newton was introduced in 1913 by the Western Cartridge Co. Until the 264 Winchester Magnum came along in 1958, this was the only American designed 6.5 mm to be offered on a commercial basis. The 256 Newton is a good cartridge and is adequate for practically all North American big game, but it is not as effective as the 270 Winchester. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.