If you check out
Hodgdon - The Gun Powder People you willfind a number of standard pressure 38 Special loadings, particularly Titegroup, that push a 158 grain cast bullet at 920 fps or better. If you check out the +P 38 Special data you will find a number of loadings of jacketed bullets that exceed 1000 fps. At one time, I found +P 38 Special data for cast 158 grain bullets with Titegroup at nearly 1000 fps, but I can no longer find that data.
My K-guns consistently like 357 cases loaded with 140 or 158 grain jacketed and Unique powder to about 1050 to 1100 fps. If I can accurately push a 158 grain cast bullet at 920 fps or better, then why waste the jackdeted bullets? I am so pleased with the accuracy and velocity that I get with 158 grain cast with Titegroup in 38 Special cases, that it has become one of my standard loadings.