Try 8.0 grains Unique with a 140 grain bullet.
I have used it for years.
Lyman #47 shows:
7.0 starting load giving 949 FPS in a 4" barrel.
8.9 grain MAX load giving 1,233 FPS @ 40,000 CUP.
This is over the current SAAMI standard pressure for the .357, but should be safe in any good .357 revolver.
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