I've been working on cast loads for my 9mm's. Heretofore, I found that 4.0 grains of HP38, under a 125 grain cast boolit, OAL= 1.10", Win. SP primers and mixed brass works VERY well. 1" to 2" groups at 8 - 9 yards. I've tested with 0.356" and 0.357" dia. boolits....and found no real difference. I have ascertained that my barrels are (all) nice ones, all coming in at around 0.355" (groove diameter).
Today, I tried some loads with Bullseye, which is the powder I use predominantly for 38 Special. I tried 3.3, 3.5 and 3.7 grains. Though all three loads weren't bad, 3.7 grains gave the best results - 2" or smaller groups, also at 8 - 9 yards. I intend to do a bit more with this load, perhaps push it a bit, to find the top end. However, I don't really think that much will be gained by this. So, for now, this load consists of a 125 grain (0.356") boolit, over 3.7 grains of Bullseye, OAL= 1.10", Win. SP primers and mixed brass.
I offer this info, in case it helps anyone trying to find cast loads for the 9mm. After always hearing that the 9mm is hard to load (cast boolits) for, I expected real difficulties. Not so - it has been easy. I would encourage anyone considering hand loading cast for the 9mm to push ahead - as I said, it isn't really tough to find good loads at all.