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I brazed a ball bearing in the end of a steel rod and used my drill press to push it down on a bullet. Fortunately I have access to about a million dollars of measuring equipment so checking the size of the dimple within a few .0001's was no problem. I don't know how accurate my rudimentary hardness checking methods are, but I can definitely measure a significant and consistant difference in the hardness of water quenched bullets versus air cooled bullets. Absolute accuracy to the Brinell scale is not as important to me as is the relative hardness of one bullet to another.

My question is "why are water quenched bullets harder than air-cooled bullets?" I have read a little bit about what happens to the iron and carbon molecules when water quenched,d thereby causing the increased hardness. But why does this happen with wheelweight alloy? What is going on at the molecular level that causes the water quenching to produce a harder condition? Is there a similar situation with the antimony molecules fitting inside the lead molecules as the lead temp rises? Anyone have any reference material on this?
 

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I can't scientifically answer that so let me make it more difficult. ;D
1 Did you cast these bullets and if so at the same time?
2 if you bought these bullets they could be different alloy?
3 would you see a difference if you hack sawed the bullets in 1/2 and tested the core ?
Have you quenched in motor oil to see what that does ?
and hammered on 1 to see what that does ?
If no to any of these could you melt some lead and test them in a consistent format.
Anyway I ain't much help but some of the bullet casters around here will have better answers...Or more ????
 

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This is it in a nutshell

When water quenched, the lead alloy particles lock or freeze together in an uneven random sequence, and do not allow themselves to slide past each other as easily. A air cooled bullets molecules are aligned and can slide past each other easily.

Think of pea gravel, it never can pack in like gravel with irregular surface and uneven sizes. Or if you were building a brick house, would it be stronger if you laid the brick so that the mortar seams lined up or did not line up?

That's it on a molecular scale. You can muddy it up with ten dollar words, and advanced chemistry and physics, but who has time for that? I am casting bullets!
 

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RIF,
That is so simple it is the best answer.
 
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