It's unfortunate that the newer cartridge references have left out the really old ones.

It does sound like you are over working your brass. The references in Masterpiece's post suggest to use a .38 S&W sizing die as this is closer to the original .38-44 target diameter used by S&W. This was way before S&W made the .38 spl. based on the Colt .38 Long which was a smaller diameter. This should also help cure your "sooting" problem.

The old S&W "target" cartridges were actually very unique. They were the full length of the cylinder but could be loaded to power levels anywhere the shooter desired, from flush to the mouth down to the base. Keep in mind that the brass used then was of the old balloon head type and did not get thicker near the head. If you want to reproduce the old gallery loads with new brass you will need to inside ream the brass.