Shrinkage

[mattd]

Man, I'm struggling to get this to work. My lee 44 mold was making undersized and out of round, .005-007, bullets. I think it's an alignment pin issue. I've been playing with the pins, as well as lapped one of the 2 cavities. Now I get .003-.004 out of round bullets and the ones from the lapped cavities come out .432-.436. Thought I could size them to .431 and life would be good, so I pan lubed em and waited for the sizing die.

A week later I got the lee 430 sizer and honed it out to .431, verified with a soft slug. Thought I would pass the bullets thru and finally have something that didn't lead. But I got hardly any resistance going thru the sizer. Measured and, except at the seams where they did size, they are undersized - .4295 - .431.

Casted a few more and measured an hour after the pour and they are big - .432-.436. So I guess I'm suffering from shrinkage. Up to .006!!? Measured some 40s that came out of the same batch. Previous they were .401, perfect. Now they are .400, too small.

Is shrinkage something you have to allow for? So I have to lap my cavities to .434+, wait a week and then size?

Alloy is 50% #9 mag shot 50% lead mixed then 2% pewter added.

[44man]

The hardest thing to do is to get round boolits from lapping a mold. The blocks will not close and you get a lead-lag at the edges.
Boolits only shrink when they cool in the mold. Just normal cooling of metal. Let them sit and age and they will expand with your alloy.
The best thing to do with an out of round or undersize mold is to send it back. You can't fix it. You seen the results of larger at the seams and that is common with molds cut with a cherry too.
Another thing, when the mold gets too hot, the seam portion will get larger but the rest will get smaller. BOOLITS GET SMALLER WITH OVER HOT MOLDS. Frosted boolits will be smaller and more out of round.
Everyone has seen a boolit that touched the size die on one side of the seam. That is because a cutter will hit the edge of the next block as it exits the first block in rotation. Lead-lag!
Every single mold is cut cold so when you heat it, the block metal expands to the edge and the boolit will be smaller 90* to the seam.
So hard to explain you are not working with a hole in the center of a block of metal, you are at the edge.
Any mold that makes a round boolit will measure larger 90* to the seam. I do it by getting my mold hot to casting temps and drop the cherry back in to cut more metal by hand with a wrench.
Are you having fun yet?