Thread: Lapping Mold

Ok, I think I may have ruined my mold. A few weeks ago I lapped my 312-185 mold to try and get it anywhere from .313 to .314. I followed all the advice online and at first it seemed to work. I lapped the first cavity, compared it to the second cavity, measured and showed a .002 increase so lapped the second cavity exactly the same as the first. Today a decided to cast some bullets to see how well the lapping worked, and to my surprise the bullets are coming smaller not bigger. Before lapping my casts would come out .311 to .312 but today they were coming out .309 to .311, WTF. I did notice my Lee melter was pouring a little slower than usual, wondering if that had something to do with it, lead not filling the mold properly? After trying to clean out the pourer with a paper clip as Lee's suggesting I got the melter to pour out a little faster but made no difference to the casts. Any advice?

Are you using the exact same batch of lead? Different alloys will shrink more/less.

Originally Posted by Makros

Are you using the exact same batch of lead? Different alloys will shrink more/less.

Yes

Temperature of the furnace and mold the same as before?

Originally Posted by rupert

Temperature of the furnace and mold the same as before?

No thermometer but I believe so. I did turn it higher than the last time I used it but not difference

Well, there's no way you could have lapped them smaller

Lots of things could be going on
Have you zeroed your calipers correctly 1st thing

Mold temp plays a big part
As does pour speed a slower pour will produce a smaller bullet
(Not 2 thou though) maybe half a thou
Maybe try getting your alloy a bit hotter
And make sure the mold is completely clean if you think it’s clean clean it again
I don’t believe in smokeing moulds a super clean mold always produces the best bullets for me

Originally Posted by makka

Well, there's no way you could have lapped them smaller

That's a trick I would of loved to know when I was at work some nights

Originally Posted by No good names left

That's a trick I would of loved to know when I was at work some nights

It would have got me out of trouble a few times!