I've noticed that some guns act differently than others in this regard. I have had many rifles put the first shot from a CLEAN barrel a bit away from the group until after the barrel was fouled. It then would group as expected. Try leaving the barrel fouled, let the gun assume ambient temp., and try it again. If it groups to your expectations, then the answer is to leave the barrel fouled until your hunt is finished. If it continues to act as before, then perhaps some of the others on here will be able to help. ( I'd like to see an answer to this myself.)