I have a old Lyman 358429 2 hole mould that I have always had to "Beagle" to get the right size bullet. Today I cast a few more and they were oversized. I gripped the mould handles as hard or harder than normal, ran the same temp lead as usual. The only difference is a new hotplate that gets hotter than the old one. Bullets aren't wrinkled but I'm sure the mould is hotter than it used to be. Does this sound possible?
Mould Temp effect on bullet diameter?
- Thread starter Rex
- Start date
With steel you get into a phenomena where the mass of the object dimensionally grows .00001 for each degree Celsius temperature the heat within the mass increases. (This is a general value and varies with the alloy.) As the mold warms and stores heat with the blocks, it continues to grow. The heat transfers within the block and stabilizes at the initial casting when you're getting good bullets. But the heat within the block continues to build up as you cast and the mold slowly grows in almost infinitesimal amounts. I theorize using the the warming plate initially adds the extra heat to grow the mold slightly before you start and give bigger bullets at the outset of casting.
I've seen this when I tracked each bullet from the mold as I cast. I'd read where some old-time Schuetzen shooters shot their bullets as they came from the mold and wondered why. The bullet gains 0.5 grain in weight and the edges are more fully defined as you cast. The radius grows .0003 to .0005 also in a run of 300 bullets. This is measuring bullets in groups of 20 and using the mean value for weight and diameter.
I've seen this when I tracked each bullet from the mold as I cast. I'd read where some old-time Schuetzen shooters shot their bullets as they came from the mold and wondered why. The bullet gains 0.5 grain in weight and the edges are more fully defined as you cast. The radius grows .0003 to .0005 also in a run of 300 bullets. This is measuring bullets in groups of 20 and using the mean value for weight and diameter.
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Eagle223usa
Active Member
I wonder if that would work the same in fahrenheit? We don't use them metrics on the homestead...
Yes. Heat, pressure, and movement are universal in the Universe.
JonB
Halcyon member
This has been my experience also. I posted about this a few years ago in regards to a Lyman 410610 2 cav mold. If I cast with a cool mold so bullets are shiny, the GC shank is large enough to be a royal PIA to install a GC. If I get the Iron mold hot, so the bullets drop with a overall frosty look, the GC shank is smaller, so GC's go on like they are suppose to, easy, yet firm. I think I posted the size differences in that thread.