So I've been casting for a few months now and after perfecting my 45 bullets I've since moved on to 9mm. I'm using a lee 128gr tumble lube 6 cavity truncated round nose mold. The boolits are dropping at a about 130-134gr and 3.56-3.59 in diameter. I'm sizing them with the lee 356 sizing die and lubing with alox. My 356 die was sizing the boolits to 354 and after more research found out that I needed to sand the die and open it up a bit more. I did that, I opened it up to .355 and still got leading. I opened it more to 355.5 and still got leading. Then opened it to 356 and still got leading. The leading wasn't as bad as before but it was still clearly there.
I've slugged my beretta 92 and found that the barrel is 355 so I didn't want to go any bigger than 356. The next thing I was going to try is polishing the barrel with jb bore bright because I was told that would help. If this doesn't fix the problem what should I try next? Could it be the load data? Or maybe the alloy? Or is there something more basic I'm missing here.
The alloy I'm using is 50/50 pure lead/ww. I'm loading with 4.2gr unique @ 1.095 oal.