Back in the summer of 1975, I spent a few hours in Les Bauska's shop in Kalispel Montana, straightening muzzleloading barrels on his barrel bending machine. It had a couple anvils with what looked like belaying pins handing down - all mounted on a finely threaded shaft about 3" in diameter for strength. When mounted, the muzzles were pointed up towards a dirty window, apparently letting in just the right amount of light. The bends were easily seen and "taken out". It was fun - for a while.