The guys I shoot with that have 6mm's are going with those or the 115 DTACs. From what they tell me, get them to 3025-3050 fps, anywhere from .020-040 from the lands and they will shoot lights out.
H4350
Imr4955
Imr4951
Out of a 6 creedmore, these are the powders I know he has found good loads with.