.257 Weatherby Magnum
Date: Nov 05 2013
The .257 Weatherby Magnum dates back to 1943 when Roy Weatherby began experimenting with the .300 H&H Magnum case for a series of wildcat/proprietary cartridges. By blowing it out with minimal body taper, adding a unique double-radius shoulder, shortening the case to 2.549 inches and necking it to accept .257 inch bullets, the .257 Weatherby Magnum was born. With 115- to 120-grain bullets, velocities hover between 3,300 and 3,400 fps, while 100-grain bullets reach over 3,600 fps. The result is an extremely flat shooting cartridge that produces comparatively mild recoil and is an excellent choice for deer and antelope in open country. When loaded with premium bullets that offer deep penetration, it is capable of cleanly taking elk. With lightweight Hornady bullets, such as the 75-grain V-Max or hollow point, and even the 87-grain Spire Point, it is a spectacular coyote rifle, offering laser like trajectory. In 1994 the .257 Weatherby Magnum became an industry standard cartridge, with a maximum average pressure limit of 53,500 CUP.
Handloads in a Weatherby Mark V test rifle provided excellent accuracy with many loads grouping under 1-inch at 100-yards; select loads clustered around .5 inch.
Avoid reducing loads below "starting" powder charges, especially with ball (or spherical) powders as pressures and velocities can become erratic. None of the maximum loads listed exceed industry pressure guidelines.
The .257 Weatherby Magnum thrives on magnum powders, with IMR-4350, IMR-4831, IMR-7828ssc; Alliant RL-19, RL-22, RL-25; Accurate Magpro and Hodgdon H-4831 each producing notable results.