I believe the twist will be 1:12" but it may be 1:14" instead. With any bullet up to 55 gr., you should be OK, but anything over that will be iffy and you'll just have to try it to find out. I've been able to get 4 out of 5 shots to go sub-MOA, but a loose trigger nut (me) keeps throwing the last one with mine. Rumor has it that the T/C Factory .223 Rem. barrels are real picky about the loads they want to shoot. I've only found one that seems to be real good, but I plan on going back and re-trying a few since I've done some things with the trigger and gotten better grips.