Slide a piece of paper between the barrel and stock. If it slides all the way to the action, shoot it twice and check for float again. I will bet my favorite rifle that the barrel is currently touching the stock somewhere. If it is touching float the barrel and shoot it again.
Sounds to me like the barrel is moving with the heat and pushing against the stock. Free floating and bedding the action should help. You can free float the barrel first and see if it helps. Bed the action if it needs more improvement.
Let us know if it is floating already or if it contacts.
You can't fix stupid....however ignorance can be cured through education!