basically what you will be doing is loading 38 special type loads in the longer 357 magnum case. I use data based on 38 special Red Dot loads .
With the 148 to 158 grain cast bullet, WC-SWC or RN , in 357 cases,
4.5 grains of Red Dot will give you a nice general purpose load , approaching 38 special +P .
For a light powder puff load target load try 2.8 grains Red Dot.
2.8 is one of my favorite loads.
Gary