Agree with Ward--
Using 231 at even the lower pressures of .38 & .38+P loads, I find that once I go over 4.7 or so grains, I get significant leading in the first third of the barrel, presumably because the high pressure is eating the bullet's hind end (also, I suppose, producing lead fumes, which I don't want to to breathe). Still very accurate at 4.9 grs, and listed at 906 fps in my Lyman handbook (from a 4" K-frame)--but I'll stick with jacketed or plated to avoid the volatilized lead.
6 grs of 231 & a 158 gr. jacketed or plated bullet make a very nice, moderate, and accurate 357 load for me.
CG