Most of the guys I have talked to, including myself, get a pretty good group with up to 120 grains, at 100 yards, but any more than that, and the groups start to separate.
I do know of one guy that can actually shoot 150 grain loads, and still keep a good group at 100 yards, but he is the only one.
I suggest as Pahoo, start low and work your way up. Somewhere in the process your sabot will break down and you will loose accuracy, and you will know exactly what your rifle is capable of shooting accurately.
Most rifles will shoot 150 fairly accurate at 50 yards, but somewhere in between 50 and 100 they lose it.