I'm still a believer in measuring the ID and OD of barrel to get wall thickness. The short coming of that method is the outside edge of the barrel where it is most likely to have been re struck to polish out a dent, is the area most likely to be thin and it can't not be read using the OD/ID measurement. For that measurement that I wish I had a thickness gauge. But as I've said before, the manson gauge remains beyond my understanding and capabilities.