Free float the entire barrel back to the receiver. The barrel is touching somewhere so as it heats up the stock puts pressure on the barrel. Look at the forearm the opposite direction from the bullet shift……
To test: fire three shots. Wait at least five minutes between shots. See if the third shot still moves. If it doesn’t, then it’s the barrel channel.
I wait 3 days and 5 hours between each shot. That way the barrel is nice and cold.
