A 26" 1-8 twist has proven to be fast enough for 90gr pills with the 22-250AI several times over. It's been my experience that you're better off with the 80's v. the 90's as the 80's shoot flatter out to around 600 yards due to the higher initial velocity and then are about dead even with the 90's at 1,000yds. Both go sub-sonic around 1,150-1,200.