A way to tell Bullet weight by hardness

[bayjoe]

I have a RCBS 40 caliber 170 grain mold.
It should throw a 170 grain bullet with #2 alloy. My bullets weigh 178 grains, I also water drop
I pencil tested the lead ingots and they are around 12 BHN
Is there a way to tell by how heavy your bullets drop to approximately how hard they are?

[Bad Ass Wallace]

Yes there is! Cast a good boolit from pure lead, then one with your favourite alloy and weigh the boolit. Divide the weight of alloy over pure to get a % difference.

If pure lead is taken as 100%, adding tin and antimony will make it lighter. 96% will be 92-4-4 and 92% will be 82-2-16.

Knowing this ratio, you can at any time duplicate an alloy that works in your rifle or pistol.

[garandsrus]

It’s not that easy.

Here is a good article: http://www.castpics.net/subsite2/Classics/Determining%20Alloy%20composition.pdf

[Conditor22]

Poke around here http://www.lasc.us/

[Dusty Bannister]

"Is there a way to tell by how heavy your bullets drop to approximately how hard they are?"
You are presenting two different questions here. Let's look at this first. Antimony is about three times as hard as tin when in an alloy, yet weigh about the same. So that is not likely to be workable.

"A way to tell Bullet weight by hardness"
Sort of a backward method when just using the scales will tell you the bullet weight without all the monkey motion.

[JonB_in_Glencoe]

The answer is no.

[sutherpride59]

If you have 100% control over your alloy make up then you could in theory but in real life theory falls apart. Buy the cheap lee tester and be happy with having a much better idea rather than doing math and hurting your head with all the complications.

[Don1357]

Take a clip-on wheel weight boolit, bhn around 10. The same bullet heat treated would be the same weight but around bhn 22.

Some alloys age harden, some age soften without either changing their weight.

[dverna]

I must be missing something...but I would not care if a bullet weighs a bit more or less than the mold is designed to drop.

KISS.

Anyway, of you must, you need to know the composition of the alloy used to spec. the mold and the composition of your alloy. Hardness is not a factor in establishing density but a result of how much tin and antimony is in the mix. Although Sb and Sn are close in atomic weight and about 60% of the mass of Pb, they affect hardness differently.

[mdi]

The answer is no.

I believe Jon is correct. I read the question as "can you determine the bullet weight by how hard it, the alloy, is?".

[waksupi]

I suspect the OP was expecting the mold to drop the exact weight it is specified for. They don't, or are very rare if they do.

[fcvan]

I drop my loaded boolits into the weapon and tell them to hit the bullseye. If I don't hit the X ring, I know the boolit was hard headed.