A fully stress relieved barrel, installed in a lathe, heated up to 140 degrees Fahrenheit will droop down approx. .006" --- though a barrel --- whose bottom is insulated by the stock from heat dissipation...will rise vertically
approx. .006" at 140 degrees Fahrenheit. That should not have much effect on accuracy at 140 degrees, but if the expanded barrrel comes into contact with the stock forearm --- it will have an effect on barrel harmonics.