Speer and Lyman reloading manuals have accurate data on cast bullet reloading data. You can also search the sassnet.com forums for what cowboy action shooters, like me use. All of our bullets have to be cast lead with pistol velocities no greater than 1,000 fps. I just bought the 358-125-RF 6-cavity 125-grain RNFP mold but have not had good weather for casting.
Thats a great bullet. For the .357 I like the 158 grain SWC from Lee also. A two cavity mold costs $20.00. If your not competing you can turn out a crap load of bullets in a day.
Between my daughter and I we probably run 10,000 rounds a year down range of the Lee 125 RNFP. Cowboy shooting eats ammo like it free. Wait.... it almost is.