As others have said it is not a problem.
I run about 50-75 rounds a week for about 2 years now. No problem. Most say no chokes tighter than Mod and that choose 1 choke size bigger when shooting steel. IE Mod with lead = Imp.cyl with steel (think that is right).
It is my understanding that the shot stays in the wad until it exits the barrel. So unless there are different wads for steel and lead there should be no additional wear there.