.257  Ackley Improved

.257 Roberts vs .257 Ackley Improved


Q: How much capacity would I gain by having my Remington Model 700 Classic in 257 Roberts rechambered for the improved version? How much more velocity could I expect to get? What is the best powder for reloading the Ackley version? Can it equal the ballistics of the .25-06? Or would I do better to rechamber for the .25-06? I know you are a great fan of the standard Roberts, so what would you recommend?


Philip Cox


A: In my opinion the .257 Ackley is badly overrated. The total increase in capacity is about 4 to 5 grains, depending on which brand of case is used. It burns roughly about 8 to 10 percent more powder to increase velocity around 5 percent. With modern powders you may gain 100 fps with a 100gn bullet. Any further increase is only gained by loading to higher pressure. The best powder is AR2213Sc, but Re-19 also works well. The .25-06 which holds another 8 or 9 grains of powder outperforms the .257 Ackley by about 200fps. Of course, you could have your rifle rechambered for the .25-06 Ackley which treads close on the heels of the .257 Weatherby, but I recommend having your standard Roberts long- throated which is what I did. Then you can seat your bullets out to gain a reasonable amount of velocity without increased barrel wear. In my rifle 52gn of Supreme 780 drives the 100gn Speer at 3110fps; 49gn of Re-22 gets the 115gn Barnes TSX going at 3050fps; and 49gn of Supreme 780 has the 117gn Sierra doing 3000fps – from a 550mm barrel. I am happy with those loads, but if you want to get ultra-high velocity try the .25-06 Ackley.




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Nick Harvey

The late Nick Harvey (1931-2024) was one of the world's most experienced and knowledgeable gun writers, a true legend of the business. He wrote about firearms and hunting for about 70 years, published many books and uncounted articles, and travelled the world to hunt and shoot. His reloading manuals are highly sought after, and his knowledge of the subject was unmatched. He was Sporting Shooter's Technical Editor for almost 50 years. His work lives on here as part of his legacy to us all.