It's called HP-38 for a reason. Because it works SO well with .38 spcl(don't really know if that is why it is named that). I load all my .38 with it or its identical mate-Win231.
You can use HP-38 for light .357 loads, but I prefer my .357 a little hotter. I use H110 or 2400 depending on the bullet size. According to the Hornady manual, lighter bullets achieve more velocity from 110 and heavier from 2400; however, they are similar and their is some economy differences between these two for these velocities.
NRA Member - Endowment Life