I recently did some experimenting with my 38 specials and wadcutters using wadcutter brass.
I aquired some R-P wadcutter brass in enough quantity to make it worthwhile from a couple of members on this forum(thank you gentlemen). I loaded them with either 3.2 grains of Bullseye or 3.3 of WST under a 358495 Lyman boolit. I already had some mixed brass loaded with the same boolit and powders. Next stop, the indoor range.
I used my Smith&Wesson Target Masterpiece with a 6 inch barrel as my test gun. The cylinder throats and the forcing cone/barrel are perfectly set up for cast boolits. I shot from a handheld rest on sandbags. I had 50 rounds each of mixed brass with Bullseye and WST, 50 rounds wadcutter brass with Bullseye, and 50 rounds of wadcutter brass with WST.
After firing 6-12 round test groups all afternoon at varying distances to 25 yards, I found that the wadcutter brass gave me noticeably better groups than the mixed brass did. The wadcutter brass groups were consistently about 25% smaller than the mixed brass groups. Sorry, I didn't save the targets.
It didn't matter which powder was used. Both powders gave the same group size with the respective types of brass.
Now all I need to do is test a couple of different wadcutter styles to see if there is any consistent improvement depending on style of boolit. I have several to choose from.