I have decided to put a aftermarket barrel on my savage 110 FCP currently chambered in the 338 lapua. I have decided to stick with the 338 lapua . I have decided to go with a prefit shilen barrel that they are going to chamber for a 250 grain berger bullet. What twist rate , diameter , groove, and length should I go with ? I really don't care about weight but will be hunting with it but can drive very close to hunting spots. How much of a difference in fps and accuracy should I expect over the factory 24" + 2 " brake?