Source(s): Newton Arms Company Catalog. 14th edition, 1920. IN Barnes, Frank C. "Cartridges of the World" Digest Books Inc., 1972.
The .256 Newton is a high-velocity rimless cartridge and was developed by Charles Newton in 1913 in conjunction with the Western Cartridge Company. It is a 30-06 Springfield cartridge, shortened and necked down to .264) with a different shoulder angle. However, the .256 Newton and the .30-06 are not interchangeable. The .256 Newton and the 6.5-06 are not interchangeable.