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pamtnman, SKB
Total Likes: 10
Original Post (Thread Starter)
#591837 02/10/2021 11:16 AM
by pamtnman
Does anyone have a formula for calculating lead alloy bullet weight? For example, I have two .400” bullets each 0.900” long. One is pure lead and weighs 278 grains. The other weighs 228 grains, and I’d like to figure out its likely lead alloy content.
Math was never my strong suit, so forgive me if the formula for solving this is easy.
Thank you math geniuses in advance
Liked Replies
#591847 Feb 10th a 12:55 PM
by ClapperZapper
You have to know what the other constituent metal was, otherwise all you can say is one is more dense than the other.

If, for example, one component was tin, and for all intents and purposes the only other component was lead, then you could figure out the percentage of each in the alloy pretty easily. Because we know the density of tin, and we know the density of lead.

It’s what is called a weighted average.

But it gets considerably harder, if there are multiple alloying components.
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#591854 Feb 10th a 02:57 PM
by keith
ClapperZapper is correct. It is very simple to calculate the volume of your bullet, knowing how much it weighs when cast of pure lead. But there are so many alloys used as bullet metal, that you would need to have an assay done to know the exact composition of your unknown alloy.

But you may find what you are looking for here:
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#591860 Feb 10th a 03:43 PM
by BrentD
yes, it is easily done IF it is just lead and tin. But in all likelihood you probably have antimony in there too and that means you have 3 unknowns and only two independent equations. In other words, "What ClapperZapper said".

I calculate lead-tin ratios for casting all the time and have a spreadsheet set up for it to make it simpler, but it's only good on PB/SN alloys.
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#591872 Feb 10th a 08:17 PM
by skeettx
The easy way, take it to a friend who buys and sells gold.
Ask him to run it through his mass spec
Then you will know

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#591896 Feb 11th a 01:00 AM
by ClapperZapper
50/50 ratio by volume

Pure Pb bullet is 1.59cm3, unknown bullet is same volume

50% Pb by volume in unknown mix is .795cm3 x 175.03gr/cm3 = 139.14gr
50% Sn by volume in unknown mix is .795cm3 x 112.12gr/cm3 = 89.13gr

Pb + Sn = 228.27gr for approx same volume bullet
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#592021 Feb 12th a 07:45 PM
by ClapperZapper
[spoiler][/spoiler]Guys, I put everything you need to know in my post.

I put the density of lead and tin in their grains per cubic centimeter, I provided the volume of the bullet in cubic centimeters and did the math for you.

I don’t think any of you read my post that showed that the bullet in question is a 50-50 mix of lead and tin by volume.

There is the small possibility, that because of the shape of the lead atom that the tin atom might be able to hide within the matrix to some degree, resulting in a decrease in volume with a mixture of the alloy, But I don’t think so.
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#592025 Feb 12th a 08:14 PM
by Parabola
Are we not missing the known unknown?

Pamtnman in his post on 10th February says the “original bullet has the copper peg in the tip”.

If, as I take it the bullet is for a British black powder express rifle, the “peg” is likely to be the closed top end of a copper tube, extending perhaps half way down the bullet and filled with air (or perhaps fulminate?) to promote sudden and violent expansion on impact.

In case it is fulminate I would suggest not trying to dismantle it.

The hollow is likely to be at least the volume of a 40 grain .22 bullet (perhaps narrower but longer) and would easily account for the difference.
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#592263 Feb 15th a 09:05 PM
by Steve Helsley
Steve Helsley
"I took the 230-grain shell to be an explosive shell." -- Why?

British rifle ammunition for the 450/400 3 1/4" cartridge was made primarily (and perhaps exclusively) by Kynoch and Eley.
Their early 20th Century catalogs make no mention of an "explosive shell" nor does Fleming in "British Sporting Rifle Cartridges."

Can anyone cite a source for explosive bullets in British commercial metallic sporting rifle ammunition?

Explosive bullets are historically associated with Sir Samuel Baker and George Fosbery. In Baker's case, his bullets were being
launched from a 4-bore barrel. A detailed study of explosive rifle bullets used in the Civil War can be found in the journal of
the American Society of Arms Collectors. They were used to shoot at observation balloons in WWI and Germany experimented
with the B-Patron in WWII. If they were ever practical - as bullet size decreased, they became impractical.

Pantaman - suggested topic for your next investigation. Weight of the priming compound in the No.40 Berdan primer.
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#592402 Feb 17th a 12:57 AM
by Mike Rowe
Mike Rowe
Steve, no theory about the 1 in 12 mix. It's on the Kynoch factory's blueprint.
1 member likes this
#592303 Feb 16th a 04:13 AM
by Steve Helsley
Steve Helsley
First - the 12 to 1 theory is not mine.

I assume that there are two reasons why Eley or Kynoch wouldn't want the bullets to be any harder than necessary -
expansion in the target is one and the other is cost (tin being more expensive than lead).

The "cup" in the base of the bullet should be for the twisted end of the paper patch.

In my 'ill-spent' youth I made explosive Minie balls. They worked.

I am a fan of Baker and have studied him extensively (including corresponding with his great-great grandson who lives in England).
I am convinced he used explosive bullets but his descriptions don't 'add-up.' He described using a 1/2 pound (3500 grains) bullet
with either "10 drachms of powder" in the bullet or as the propelling charge. In my 8-bore, I used 10 drachms (280 grains) of powder
behind a 1605 grain bullet that produced a velocity of 1040 fps. That charge behind a bullet weighing more than twice as much, in a larger
diameter barrel, would produce an anemic velocity. If Baker meant that the 10 drachms was the explosive charge in the bullet, by
volume, it would displace 2000-grains of lead unless the bullet was substantially lengthened. Seems like a great project for "Myth Busters."
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