For dispute settling between manuals with any Hodgdon, Win or IMR powder I go here: http://data.hodgdon.com/main_menu.asp

Here's the 158gr data for 231:
158 GR. CAST LSWC Winchester 231 .358" 1.475"
3.1 782 11,900 CUP
3.7 834 14,600 CUP

158 GR. HDY XTP Winchester 231 .357" 1.455"
3.8 661 12,600 CUP
4.3 779 15,900 CUP