I would also agree with the heat issue, but I am also wondering how well does it shoot at a 100 yrds,and what kind of numbers are you getting out of your load, S.D. if your S.D. is not in the single digits this could also be part of your problem as well, if your 100 yard group throughs one low once in a while you could also have a load issue.I have a factory model 70 win that is a feather light and it will hold 1/2 moa at a 1000 shooting a 5 shot string then it needs to cool back down,
Wld be my S.D? It holds a sub zero group at 100 yards, ii can make all 3 in a group touch with it.