I have always just slid a 3x5 index card between stock and barrel with cold barrel. It slides all the way up. How do I know that after a couple shots when the barrel heats up it does not make contact during the vibration or whip. I am going to check with a hot barrel next time but lets just say the card slides all the way up, how do I know there is no contact during the shot? Using factory stock by the way and I know it would be easier to put a after market on and glass bed it but that would still not answer this question. How do you know what happens during the shot?