Just a couple quick thoughts on this subject. I saw a show on TV some years back where they were installing a huge ball in a socket for an aircraft wing, they froze the ball part in liquid nitrogen and heated the socket part in an oven and were able to insert the ball in the socket that way, once the parts reached the same tempeture the ball expanded and the socket contracted to the point where the ball was able to move in the socket but not come out. Anyway I was thinking one could surround the barrel with dry-ice and heat the frame a little but not too much and it might be enough to remove the barrel that way.
In looking at a schematic for the Pietta 1858, the barrel has a shoulder where just ahead of the threaded round section that screws into the frame the flats begin. Isn't that flat section supposed to butt up against the flat section on the front of the frame? Backing the barrel off to align the sights would create a slight gap between the barrel flats and the frame. and also open up the barrel cylinder gap. I don't know how they align the barrels at the factory. Just some thoughts anyway.
