I am posting this based on a response to my post in the hammer gun folder, so as as not to hijack the original thread. My joking comment was about a pocket sized wall thickness gauge, since I have passed on a couple hammer guns ( a Parker lately and an interesting early German piece last spring) since the I had no way (neither was at a gun shop or show) to determine the safety of the barrels.
The Manson tool was recommended and really looks like a reasonable alterative, not too expensive and small enough to keep in the truck and carry into an antique show just in case. I felt bad about the Parker, at a give away price, but I could tell the tubes had been cleaned up, how much was the question.
So--My question is for anyone who may have one is --> do you need a vise to work it accurately? The description on the Brownells website references mounting it in a vise, The tool I can haul around all day, a bench vise, maybe not.
And of course have a tool like that handy will mean I will never have the chance at a piece like that again