Have you tried any other projectiles other then the powerbelts? Perhaps your rifle does not like the power belts.

I personally would suspect that the rifle has some problems somewhere else. You could also try sending CVA a email and tell them of your problems and see what they suggest. Although they might tell you that 4" is acceptable. But I agree with you, acceptable to who. That's plenty good for deer shooting if you are sure the shots will hit in that 4" circle..