My most accurate (and mild) .357 load is 11.5gr 2400 behind a 158gr plated RNFP from Xtreme. Can't tell 'ya the exact OAL right now, but those particular Xtreme bullets have a cannelure, so I just seat them to the top of it. I have always read that plated bullets are closer to lead than FMJ bullets as far as loads and performance are concerned. These are very accurate out of my 6" 686+.
The few other powders that I have used for .357 don't even come close to what the 2400 load does for me.