Most of them will not reliably feed .38 wadcutters or semi-wadcutters (due to the shape of the nose of he bullet.) You would have to load these one at a time, right into the chamber.
Also, the .38s hit almost 6 inches lower than the .357 mag rounds. So, the problem is that if you sight in for .38s, you are going to have to do some real serious adjustments to get it back on center for the .357 mag (which is the round for which it was truly designed.)
Regards, Mannyrock