2.7gr of Bullseye under a 148-gr wadcutter, or 2.8 gr under a 158 LSWC, will do what you want. Chrono'd velocities in some of my revolvers are staggeringly low:

578
591
607
615.4
597.5
Average: 597.78
ES: 37.4 (6.26%)

The load is reliable, I've produced thousands of them.