Q: How does the .257 Ackley Improved compare the .25-calibre rounds like the .25-06 and .257 Weatherby Magnum? I’ve read a good many of your coverages of the various .25s, but the .257 Ackley has apparently escaped my attention, at least in Sporting Shooter.
Arthur Douglas
A: The .25-06 and .257 Weatherby are capable of shooting .25 calibre projectiles at higher velocities than is possible with the .257 Roberts Improved simply because they have greater powder capacity. The .25-06 gets the 100gn bullet moving at 3300fps while the .257 Weatherby gets it out at 3400. The .257 Roberts Improved is a more efficient cartridge, however, because it is considered to be maximum case capacity for the.25″ bore size. The higher velocities achieved
with the larger .25-06 and .257 Weatherby are achieved at the cost of much heavier charges and shorter barrel life. For instance, a maximum .257 Improved charge of 51gn of RE-19 pushes a 100gn spitzer along at about 3100fps, while it takes 67gn of RE-22 to get 3400fps in the .257 Weatherby with the same bullet weight. In all honesty I cannot see any worthwhile gain by improving the .257 Roberts. My Ruger Roberts is long throated and it takes just 49gn of AR2209 to drive the Barnes 100gn TSX at 3236fps from a 22 inch barrel.
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