Here's my 2 cents on the Zero 148gr. HBWC:

If you are determined to use W-231, a loading of 3.1-3.2gr. is optimal. Another excellent powder for this bullet is VV-N310. I currently load 3.0gr. of Titegroup for this bullet, as this powder has a slight edge in accuracy at 50 yds. slowfire over the VV-N310. These loads have been developed for a model 14 bullseye revolver.

All of this said, there is more than powder choices involved in developing a tack-driving load for the Zero 148gr. HBWC. I have a custom seating die just for this bullet, that only contacts the edge of the bullet's nose. I load this bullet a bit longer than most........COL is 1.160 with brass length of 1.145. I use a Redding taper crimp die to finish off the round. I get zilch leading with this formula. I believe that many leading issues with swaged bullets are caused by using a roll crimp(no matter how mild) that scrapes off a bit of lead as the bullet exits the case. You don't need no stinkin' roll crimp on a swaged bullet that has no cannelure, that is being fueled by a fast burning powder, and is loaded to pressures where "jumping crimp" is not an issue.