I take it that everything was fine when you changes back to 5.56? To be honest I didn't have a break in period with 6.8. I figured that the gun was already broken in with 5.56 so I shot a mag or so on setting 4 then tuned it down to 3 as it was spitting them way to far on 4. I think with my SBR I shoot on 2 most of the time then turn it up to 3 when it starts to get really hot. I would say to check the gas block seating on the barrel and make sure that it is lined up properly. Other than that I can't think of anything off the top of my head.