I'm going to show my ignorance here but how else does one learn?
I'm guessing here that sleeving is done by going down a ga.? 12 to 16 or 16 to 20?

My ignorant question is can a 20 ga barrel, that's in bad shape, be bored a bit and sleved back to a 20 or is there so litle metal left that it wont work?

I'm figuring it wont work but..........?