I have had two rifle now that I loaded up a series of different grain powder changes n .4 of a grain increments. When I shot the first series I would get a good group with one of the powder charges. Then I would take the rifle home clean it and make 12 rounds of the best shooting powder charge. I wouldn't change, the primer O.A.L, and I usually don't crimp rifle rounds. I would take these out and shoot 3 4 round groups and the groups would suck. I figured the first group was a fouling group and it would get better with the other groups, but that has not been the case. Anyone else has this happen? Any ideas what could cause this?
Also I shoot from a bench and use a rifle rest and butt stock bag in the back. I put the rifle on the same place on the rest and butt stock bag. Basically I'm just pulling the trigger.