Re: 22-250 build help
A 12 twist will take you to around 65g bullets. A 9 twist will allow use of long match type 70g bullets for sure. Some will stabilize up to the 75g AMAX. Some won't. An 8 twist will let you use up to 80g bullets.
If you want to go heavy and fast, I am convinced that it stepping up to the 22-250 AI is worthwhile.
You could go with a 28 inch barrel. Given the case capacity you are dealing with, however, I am not sure that it will offer much advantage.
My current 22-250 wears a Shilen 26" 12 twist barrel. It shoots the 55's very well. When they are available again, I want to try the 53g VMAX. It has a better bc than the 55's and can be pushed to 3900 or so. I have run the numbers on the JBM website and the 53g VMAX looks like it will perform very well out to 500 yards or so.
My next barrel will be an 8 twist chambered for 22-250 AI. I plan to run 75g AMAX's, unless something better becomes available.