The .256 Newton was a high-velocity, rimless centerfire cartridge based on the .30-06 Springfield military cartridge and developed in 1913 by Charles Newton in conjunction with the Western Cartridge Company.Barnes, Frank, and Amber, John T. Cartridges of the World (DBI, 1972), p.76, ".256 Newton". To make the .256 Newton cartridge, the .30-06 case was necked down to a caliber of .264 inches, the overall case length was shortened, body taper was increased, the neck was moved back, and the shoulder was given a sharper, 23-degree angle, as opposed to the 17-degree shoulder of the parent cartridge.
The .256 Newton suffered from a lack of available slow-burning powders capable of fully exploiting the large capacity of the parent case. Newton's company went bankrupt after the end of World War I and production of commercially loaded ammunition ceased by 1938.
After World War II, with a supply of 6.5mm rifles (.264 caliber), the availability of slower burning powders, and inexpensive, surplus .30-06 brass cases, shooters developed the 6.5mm-06 wildcat cartridge by necking down the .30-06 case to 6.5mm (.264 inches). In 1997, the A-Square company standardized the chambering as the 6.5-06 A-Square with the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI). Although substantially similar, the .256 Newton is not interchangeable with the .30-06 parent cartridge, the 6.5-06 wildcat chambering, or the SAAMI standardized 6.5-06 A-Square cartridge.
References
External links Information from the Reloaders Nest An online discussion archive on the .256 Newton