I typically use Berry's copper plated bullets for the 357 magnum, (approx .10 per 158 grain bullet). I've used lead but usually limit the lead to 38 special.
I got a great deal on some 125 grain HP and have been using Alliant Power Pro 300 MP powder my Hornady manual shows a maximum velocity of 1600 fps using 20.4 grains as a maximum load. The Alliant web site lists a maximum load of 22.3 grains which pushes a Speer Gold Dot at 1995 fps according to their data, I started at 20 grains and have worked up to 22 grains with no problems in my Smith 686. Holding a 2" group at 50 yards from a rest. Alliant Powder - Reloader's Guide