Well, I took a crack at it. Someone (Mike M?) suggested using a furniture clamp. I had one in the garage and here is what I have come up with: a desktop gun bench built on a 36 x 14 in birch plywood (an old piece of shelving). A wood clamp compressor with a U-bolt clamp. 3 v-notched 1 x 1,5 in blocks to clamp the tube. Still need to make a stop. Think I will try for an interchangeable set, one solid and one with a hole drilled for the barrel, depending on whether or not the barrel has been removed. The clamp has a little less than 2" of travel on the thread, but it is possible to slide the clamp mechanism back using counter pressure and carefully squeezing the slide release. Need to figure out exactly what the pusher block should look like. I put the bench on 2x4 rails on either end to raise it enough to also use my hobby vise. It should set nicely on a desktop and have room to put tool under the gun bench, out of the way, when not being used. We'll see how this works.
