I know its not a powder that you asked about, but I use 12.0 grns of IMR 4227. It is VERY accurate out of my 686, and has a very tiny orange flash in low light. I'm getting about 900ish fps (my data isn't here or I would post exact numbers)

The only issue is that load is above the 38 +p data I have, but under the minimum load for 357. So take that how you will.