In my 686 6" revolver I have used Bullseye powderin a 38 special
loading from 896 fps to a full 980 fps.

Back then there was no problem getting primers and I did find that the Federal and CCI primers did give different fps and also accuracy from the same amout of powder.

If you have a chrony and slower powders, I would cut the top end off at around 1050 fps for your best accuracy.

A Hornady XTP can be pushed about 100 fps faster but it has a heavier copper jacket for higher speeds and hunting use.

If your bullet does not have a "Can" on it, you don't need full loads
that will just cause problems with the heavy recoil, with just a taper crimp.