No-one suggested to check if there is barrel contact with the stock. Do the dollar bill slid under the barrel its length to see if ther is contact. How often do you let the barrel cool between groups? A very warm barrel can move enough to contact the stock If with the dollar bill test you would have only .003 of clearance. Check that the mounting screws are tightened to 40-45 inch lbs then do the dollar bill test again.

El Lobo