Are you saying you've tried 4 different sets of bases and rings? If you haven't tried different bases and rings that would be my next move. If you have tried different bases and rings I would tear the rifle down and start looking for problems. This is my suggestion if you decide to tear the rifle down. Mark the barrel so you know how it was indexed then tear the rifle down to look for anything obvious if you don't find anything obvious reinstall the barrel with the index mark in a different location and go shoot. If the POI changes you will know it is a barrel problem and can take the necessary steps. Hope this helps. Brian Brown.