I was pretty much set on 458 SOCOM then I ran across McGowen Precission Barrels. I see they have 450 Bushmaster chambered barrels with a faster twist.
http://mcgowenbarrel.com/
So I'm wondering if I'm wrong thinking the 450BM could use a faster twist? If I got a 450BM I'd want it to shoot 300 grain projectiles. Is the 450BM able to feed a .452 300 grain RF with a bigger meplat or 300 grain JHP?