If you are getting two good shots and then a flyer, then cool the rifle down and it repeats, the two good shots then a flyer. I believe the problem is your barrel is heating up and walking. As was mentioned earlier, try waiting five minutes between shots and see what happens. You probably did a good job bedding so at some point you might try putting some upward pressure on the barrel by inserting something between the barrel and forearm tip.(paper, cardboard etc.)
