Your tightest group is with 70.9 grs. How clean is the barrel with this load? Adding 2 grains at 72.9, I don't think you're burning all the powder and the group is much larger. I'll take accuracy over speed any day. You can also try a 210 primer and may get a more even burn rate.
I think I'll load 25 of just the 70.9 in 5 groups then clean and see what happens. I bet its just what you're thinking.
This load work up wasn't as good with gm210m.
