I use 6.5 grains of Win 231 with the 185g bullets.
You will have to test and see what your pistol likes. I would say start at 6 grains and work up to 6.5 and see what shoots best.
TS
My wife's SA Ultra Compact (3") ported barrel shoots amazing groups with 5.5gr. SWC's at 1.57" It shoots so well with it, I chose to use it when I shot my NRA pistol instructor's course/