Wacky mold that grows

Last year I bought a new .434 double cavity mold from NOE. When starting to cast from a cold mold, the first 3 or 4 bullets would drop at .434. But , as the mold heated up, the bullets drooped bigger & bigger. When up to operating temp, they stabilized & dropped at 439+ to .440, & stayed that way. I contacted NOE & they replaced the mold, no problem.The new mold works perfectly.

I still have the old mold, & guess it is only good for casting sinkers. I've been casting for over 60 yrs & have never had a mold act this way.

The alloy in the mold blocks themselves was incorrect

The thermal expansion rate of aluminum for the common mold alloys like 6061, 2024 and 7075 are so close to each other that different aluminum alloys will not have a measurable effect on the bullet size due to different alloys being used in the mold blocks.

If the bullets are out of round, it's a closing or warpage issue. If the bullets are round it's a size issue with the original mold or it a process error. Calculating the actual expansion of the cavity as it heats is simple. Once you had is the temp of the lead ally and the following shrinkage it gets a little more challenging.

https://amesweb.info/Materials/Therm..._Aluminum.aspx

https://goodcalculators.com/thermal-...C%20%C2%B0C%29.

In simple terms aluminum expands or contracts at the rate of approx. 0.000231 inches per degree depending on alloy. That does change somewhat as the temp changes. It decreases as the temp gets closer to absolute zero.

The alloy I use is the same alloy I have used for years. Scrap clip on WW from my decades old supply. This same old scrap WW cast perfect .434 bullets in the new replacement mold. This same scrap pile of WW's cast perfect bullets in all of my many other molds. Over 60 yrs of casting & I have never had a problem like this.. Molds from Saeco, Ideal, Lyman, RCBS, Lee, Accurate, & NOE. None of them grow in size as the mold heats up. It was just this one & only one mold.

Haunted mold, there's the answer.

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Originally Posted by elmacgyver0

Haunted mold, there's the answer.

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That's kind of what I was thinking, but my guess was its possessed by an evil spirit and must be punished.

Sounds like a .43 Spanish mold.

And probably haunted from the Spanish Inquisition.

https://youtu.be/Cj8n4MfhjUc?feature=shared

One of the unexplained mysteries of life!!

Spank it.

Noe may have gotten some stock that wasnt up to specs and the shrinkage/expansion was off to what they used.
Die cast dies are built with different grades of steel do to the expansion characteristics of each grade. This helps keep parts the right sizes and the die opening closing and sealing smoothly.
Materials can vary some and sometimes mistakes are made in the blending mixing. We got in several bars of O6 tool steel that every detail made from them cracked in heat treat.

Pretty interesting, thank you for sharing. I have never heard of such until now.

Sounds like that mold would work great in my 43 Mauser Rem. Rolling Block