Originally Posted by Sully2
Isnt the "06" that the 25-06 is derived from also a well known casing...maybe even BETTER known since its been around for over 100 years??
Granted ther 257 AI is one hell of a cartridge...no one can dispute that...
But looking at one of my manuals I cant find ANY 257 load with a 120 slug that tops 2810 fps and can find at least 7 or 8 loads with the same 120 slug that best 3000 fps. And ALL of those loads are using 47; 49 and 50 grains of various powders...??
In both cases you have to fireform to get their AI version so neither has the upper hand in ease of manufacture.
*well yes and no to your post. The .257 Roberts is the parent of the .257AI as we already know. But Ned made the .257 case by necking down the 7mm Mauser case. I'm not positive, but think the Mauser case predates the 30-06 case by a year or two.
* looking at the AA loading manual (first one I picked up) I see that 49.5 grains of AA4350 is good for 3020fps out of a 26" barrel (max). There's a faster load with 3100, but they don't make it anymore. This is a true Ackley case instead of the 28 or 30 degree shouldered improved case designs. 47.0 grains of 2700 will get you about 2960fps. I have two Hornaday manuals, and the older one list three rounds in the 2900 fps range using a 28 degree shoulder and a 24" barrel. Ackley also published several 3000fps loads in his books.
* Now last time I looked Forster has .257AI die sets on the shelf without having to pay the premium price for others. That's a little bit of extra cash in your pocket..
Load data for a 25-06AI maybe hard to come by (I have only one set, and it's suspect). But it's easy to come by for the .257. I personally would have opted for the 6.5-06 over the 25-06. Ackley has stated more than once that the main reason for the improved 06 case was to stop brass flow. I seriously doubt that you'll see much more than 3100fps with the improved case as it's already about as much as the .257 bore can handle.