Iron Worker,
Not sure yet, Have yet to burn out a 257 AM barrel /ubbthreads/images/graemlins/grin.gif!! That said I have several customers that have 257 STW rifles I have built for them and those using the slow ball powders are easily topping 1100 rounds of big game accuracy life and a couple are over 1200 rounds.
Those that are using stock powders such as Retumbo and the like are getting around 900 to 1000 rounds of big game accuracy.
When I say big game accuracy I mean a rifle still has the ability to easily put the bullet in the vitals of a deer size animal out to 600 yards.
If your talking about varmint quality accuracy where you need to be able to hit a P. dog at that same range, obviously the barrel life will be less.
As far as the 257 AM is concerned, using the 156 gr ULD and WC872 I am prediciting a 1000-1100 round barrel life. Again this is a prediction so I will let you know when I get there. My personal 257 AM has about 50 rounds through it and in the field its been shot once or one kill on my goat. I suspect I will rarely shoot this rifle except for occasional range practice and then serious big game hunting use. As such, I suspect it will last well over 15 hunting seasons the way I will use it which is the way the Allen Magnums were designed to be used, for big game hunting by design.
They are not the most friendly things to barrels but with the right barrels and loading componants they offer very long lifes for their intended purposes.
Kirby Allen(50)