Uberti, and I presume Pietta and others use a 5/16-18 thread on the arbor.
That's .312. Major diameter of the arbor is same as Colt at .412, so you have .050 on the radius to make a spacer. In other words, a thin shim .312 ID and .412 OD.
18 threads per inch is .055 thousandths per revolution, so, about 6 1/2 degrees per thousandth. SO, if you get the pin out, and the book says to drill with about an .090 drill, should take out the whole thing, you then tighten the arbor snugly and measure the tilt of the wedge slot, in degrees. Each 6 1/2 degrees will be ABOUT how much you have to shim. Ie, if it turns about 30 degrees off level, you'll need about 5 thou in shim to bring it back snug and wedge slot level.
That should also get the pin hole back in line. That, I would tap out to put in a "grub screw", a socket head Allen set screw. Easier to get out the next time you have to repair it.
If you don't have machinery to make the shim, you SHOULD be able to have a shim made relatively cheaply. Turn and bore a piece of steel, part it off and grind it to thickness.
This might be a temporary fix. If the threads are stretching, deforming, rather than shearing, they will do so again after the repair. Light loads, I don't mean squibs, will delay that.
Also, if your arbor bottoms out on your revolver, you may have to refit the end of it to close up the barrel lug, frame fit, since the stretched threads will make the arbor longer in effect.
Another idea I was considering is impractical, as the hammer slot is just over 5/16. Insert a barrel nut. Can't drill a hole big enough for that without opening part of the barrel slot. Heli-Coil, you have to drill oversize to tap, and get the thread start to begin just right to time the arbor slot. How to do that, I don't know. Since the companies sell ready made arbors, I assume they use CNC machines to ensure that the threads on both the arbors and the frame holes start at a precise angle. Screw it tight and the wedge slot is dead level.
A suggestion if you get the arbor out is to spin a 5/16-18 nut on it and see if the arbor threads are distorted, too. Some brasses and bronzes are as hard as or harder than some steels. If the arbor threads are stretched, replacing the arbor, for about 20 bucks, might be an option.
I recommend "Gunsmithing Guns of the Old West" to all of you, to learn about them. Long rifle and repeating rifle shooters included, and the early cartridge revolvers.
Cheers,
George
Long winded, I know. Sorry.
BTW, I have checked my sources. Frame is Part No. 1 and have yet not found a vendor who will supply one. I think cartridge gun vendors WILL sell you a replacement frame WITH a background check, as the frame is considered THE GUN. It is the part with the SN on it. You have basically bought a GUN if you buy a modern frame on which to build a custom. Barrels and all other parts are available mail order without background check.