Does anyone have these voids in the sides of your bullets like this?
It happens with nearly every cast with 1 or 2 bullets in each 5 or 6 cavity aluminum pistol bullet mold. There is no rhym or reason which cavity will get it. I’ve been fighting this issue for a long time and it seems to happen more in molds without lube grooves.
I’ve thought my alloy might not have enough tin so I added more tin and that didn’t make any difference.
So today I finally figured out the root cause of the problem. It has to do with the speed that I fill my molds with lead. If I open up the needle valve on my bottom pour Lee pot so it flows full volume this causes the voids. I think it might be filling too fast and trapping gas that is unable to vent out quickly enough. When I slow the lead flow to a very slow flow, I get NO voids at all. It’s that simple.
This may be common knowledge but if it’s not then I hope this may help those who were struggling like me.