.257 Roberts
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The .257 Roberts was originally a wildcat cartridge, devloped by N.H. Roberts; it was commercially released by Remington Arms Company in 1934. The .257 Roberts is based on the 7 x 57 mm Mauser cartridge necked down, with the shoulder angle increased from 15 degrees to 20 degrees. The cartridge uses standard .257" diameter rifle bullets.
Though less powerful than the later .25-06 Remington, the .257 Roberts was a premier medium game cartridge for a half century, and still remains popular today-especially for recoil-sensitive shooters. The .257 Roberts is also available in a +P version as well as an Ackley Improved version.