Got up to 17.0 H110 yesterday with the 158 xtp. 5 inch 627. Velocity averaged 1209 fps (seems low) ES and SD were dick nothing. Went to 17.5 and velocities jumped up to nearly 1300, but ES and SD was all over the place. Cases fell out of the cylinder, no flat primers.
Might give AA # 9 a try.
Win 296 rather than H110, but in an older Blackhawk, 17.5 grains under a 158 XTP/HP in WW brass with Fed 200 primers was the accuracy load. Absolutely clubbed the snot out of stuff, too. After the BH went down the road I used that load in a 10" TC Contender barrel .. shot very very well. It is one I keep far from my J-frame .357.
You might look at PowerPro 300 MP as well, seems to take about 1/2 grain more than H110/296 and produce a little more velocity per the load manual, haven't chronographed it. Did some accuracy work and in some instances it is pretty respectable. Blasty though. Not the solid "whack" of muzzle blast a stout 2400 load gives though, seems like nothing compares to that.
