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?
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.