Here is a suggestion, make a barrel vise. Go down to the local scrap metal dealer and see if he has a couple pieces of scrap aluminum about an inch thick. One needs to be about 4 inches long the other one about 6 inches. Then mark the middle of both pieces and saw/file or mill a vee notch in the middle of both pieces. Lay the long piece on the bench with the open vee up then center the short piece on top with the open vee down. Mark and drill a 1/2 inch hole on each side of the vee's so as to make a clamp that will tighten down on the barrel. Then find two 1/2 inch carriage bolts that you can drive into the bottom two hole of the long piece, I counter sunk mine so it would sit flat on the table. You can probably get by with two standard 1/2 inch washers on top but I bought a set of these spherical flange nuts/washers http://www.mscdirect.com/product/85577856 to go on mine, they will allow a tapered barrel to fit properly when the clamp is tightened down. I padded the sides of the vee with some type of vinyl that I had years ago, forgoten what it was but its held up for over 30 years! I use two C clamps to hold this barrel vise down. Just insert the oct barrel, index into the vee slots tighten bolts and use your long handled cresent wrench to remove the breech plug. I will try to take a photo of mine later on.
Dennis
(https://americanlongrifles.org/images/ALR Photos/vise.jpg)