I have work on a number of rifles that have had this problem; some times the if the problem does not go away with the hotter caps like the RWS1075 you need to check [especally on CVA or Traditions for a burr or a shaving in the channel of the snail] once I even found a shaving in a TC and I have had to redrill a couple of snails that were not drilled quite far enough so that there was a flange at the angle of the snail. Lee