W:
I have a 25-06 Ackley Improved, which I use with Barnes XLC (blue-coated) bullets. Using Winchester brass, Federal 210 Match primers and a maximum SAFE load of RL19, I get 3500 fps.
This cartridge is over-bore, even with the new slow powders available today. I've shot maybe 100 rounds, mostly while fire-forming the brass (from 25-06) and developing the load. Since this is my version of a cross-canyon deer and antelope "death ray" I don't shoot it that often. I expect useful barrel life will be about 1500 shots. For a hunting rifle, that is 2 lifetimes.
In my humble opinion, the .257 STW is very inefficient and would indeed be a barrel burner, leading to extremely short barel life. If you must go the belted magnum route, you would be better served with a .257 Weatherby, which is less over-bore. By the way, my 25-06 Ackley delivers velocities about 50 fps slower than the Weatherby. You can find loading data for the 25-06 AI in the latest Sierra loading manual. :wink: