If you want to chamber a barrel for a 30 BR my guess is you want to shoot bug holes and shoot 100-200 yard bench rest and if that is the case, someone has to come in last, it might just as well be you.
Ideal accuracy comes from running the slowest possible twist rate for the bullet length and velocity you are driving them at. If you spin the bullet any faster than just enough the bullet speed wobble is increased and accuracy will always suffer. A 1 in 12 is fast for a 30 cal and well suited for bullets heavier that 185 grains.
It might shoot better than lots of guns, but not as good as a half decent bench rest rifle with an appropriate twist. Off the top of my head, my guess is they gotta be using 1 in 15 twist or so for 30BR.