Having fitted quite a few barrels I've got a slightly different take than some posters.

Real briefly, the best way to evaluate the issue is to pull the barrel pin and loosen the barrel about 90 degrees. Turn the barrel in hand tight. If the (from the rear) left hand side of the barrel rib lines up with the right hand side of the frame rib, you can just turn the barrel in to proper alignment and you'll have correct torque.

If the barrel comes up short, if it's very slightly slightly short pull it and lightly apply some grease to the barrel shoulder. Be very careful in moving it to index point. Anything significant, you'll need to lightly face the barrel shoulder.This is a skill of the craft thing evaluating what you can muscle without cracking the frame.

If the barrel turns past that alignment point with hand pressure, you'll pretty much have to do the barrel set back. Kinda depends on how far past. That doesn't involve cutting any new threads, just moving the shoulder-don't forget to trim any under lug if the ejector rod is enclosed.