Jack, the prescribed (common) method is to use a barrel vise after first removing the ejector assembly. Since most of us don't have an actual barrel vise you can use soft lead in a standard vise and cover it with leather as you tighten it down on the barrel. Remove the cylinder and place the barrel securely in the vise. Once you have the barrel secure use a wooden block that fits snug inside the frame where the cylinder was housed. Since it is shooting left you will want to rotate the barrel clockwise as viewing it from the muzzle. It takes very little movement to change the point of aim. Check it often and do not over tighten.
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Gunslinger
I was promised a Shortycicle and I want a Shortycicle!