shimming will not look as nice as a custom fitted job done on a lathe, but it work just fine. No reason not to do if if you need to fit a barrel to a revolver and have no access to a lathe.
The "correct" way to do it with a lathe is to set back the barrel shoulder enough to make the sight come up to 12:00 and then cut and throat the rear of the barrel to give a .003" cylinder gap. After that you must adjust the length of the ejector rod and push rod to work because the front locking pin and lug are now moved back a bit, but that is fairly easy to do.
The only problem with shimming is that you sometimes have to make a new front locking pin. Make it a bit longer then the original so it will fully seat into the end of the ejector rod. Not hard to do, but it takes a bit more work.
You make it about .040" too long from the slot to the nose. The cylinder will not close at that point. Now you dress down the extra length and move the bevel back so it will cam past the rod on it's bevel. Pretty easy.
If you use drill steel for the new pin you can do the 'turning' with a hand drill and a file. The slot is also cut with a good Swiss file. When it's dressed to length and polished you need do nothing more. It will last forever.