That will depend on your rifle.
I believe the 4x4 .308 barrel has a 1:10" twist which is well suited for a variety of bullet weights. The Super X is built for taking down game, not for precision shooting but it will be fine for getting your new scope dialed in on paper. I shoot some of the power point stuff on occasion, but usually only for banging steel gongs at 300-500yd. If you're shooting for precision, for your barrel there's no better factory ammo to start with than Federal's 168 grain Gold Medal Match...
http://www.sgammo.com/product/feder...l-gold-medal-match-168-grain-bthp-ammo-gm308m
It's not cheap, but I'd suggest picking up a box to try next to your Super X. The results on target will speak for themselves. My 700 will put up consistent 1/2" and under groups at 100yd with the 168 grain Federal GMM, but I'd be lucky to hit a tennis ball two out of three times with the 150 grain power point at the same distance...