Pooch was wrong about measuring the outside of barrels to determine wall thickness, and he is wrong again when he says the Manson gauge is a joke. It is not a joke if you know how to use it. The vertical method has quickly become obsolete, even when used with the Gaddy modification. There is a step by step explanation of how to use the Manson in the most convenient and accurate method on the PGCA forum in a thread titled "Barrel wall thickness" page 5. The thread is in "General Parker Discussions".