Congratulations on your group. I don't shoot 8mm but according to Ken Waters' Petloads book, the lightest load he has is for 150gr SP using IMR 4350. My Lyman book suggests 14-18gr Unique with a max MV= 2150fps for a 120gr 8mm cast bullet. SR 7625 and 630 are two other powder options. All powders are also listed for their heavier cast lead bullets from 150gr to even 214grains. I hope this can be of some help.
Everything helps, thanks.
I have been unable to find any 150gr bullets at a price I want to pay currently.
That's probably a very popular weight for hunting, and it's definitely on my list, although seems the heavier I go, the better my results.