FWIW, trials by Springfield Armory, back in the development for the 30-06, determined that the 1:12 was the more accurate twist for a .30cal., but the military wanted a twist that would still stabilize the 220gr. bullet, thus the 1:10. Then they ultimately ended up using a lighter than 220 gr. bullet............
I expect yours to be 1:10, but if it was 1:12 I would be perfectly happy were it mine.
I expect yours to be 1:10, but if it was 1:12 I would be perfectly happy were it mine.