Finding approximate tin content by bullet weight

[fecmech]

Is there some way to estimate the tin content of an unknown alloy by using the bullet weight of a sample? In this case I have about 15 lbs of something I know is very tin rich, just not how much. When I cast a pure lead bullet in my H&G RN mold it weighs 160 grs. When I cast a mix of 50/50 WW/lino the bullet weighs 155 grs( this is new factory lino). When I cast the unknown alloy the bullet weighs 145 grs. Is there any way for me to get a good "ball park" idea of the tin content in this alloy?

[Defcon-One]

YES, but not if there are other metals in the alloy. If it's a binary alloy (only Tin and Lead, like 50/50 solder) it is just a bit of math:

The density of Lead is 0.409 lb. per cubic inch or (2,863 gr. per cubic inch).
The density of Tin is 0.264 lb. per cubic inch or (1,848 gr. per cubic inch).

At 160 gr. your bullet is about 0.056 cubic inches of pure Lead. (160/2,863 = 0.056....)

So, a bullet of pure Tin from your mould would be 1,848 X 0.056.... = 103.28 gr.

A bullet from your mould of the mystery metal is 145 grains.

So, (.735 * 160 + .265 * 103.28 = 144.96) Close enough to 145 for me!

Your metal is about 26.5% Tin if it is a binary alloy meaning there are no other metals like Antimony in the mix!

[fecmech]

Thanks D1. From the history of this mystery metal I 'm pretty sure it's a babbit of some kind and there may be other stuff in it but I think for my purposes thinking of it as 20% tin should work just fine. Again thank you for doing the math.

[Defcon-One]

You're welcome!

Babbitt means that it could be anything!

I learned to do this because I cant stand Mystery Metal! I gave some Babbitt away because I had no clue what was in it or what to do with it. Sometime it is better to just cast fishing weights from it and move on.

Good luck with it!

DC-1

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FYI:

There are many Babbitt alloys in addition to Babbitt's original. Some common compositions are:

90% tin, 10% copper
89% tin, 7% antimony, 4% copper
80% lead, 15% antimony, 5% tin (My bet is on this one! Hardness would be about 24 BHN.)
76% copper, 24% lead
75% lead, 10% tin, ?
67% copper, 28% tin, 5% lead

That would be a lot of math! Might want to test the hardness of your mystery alloy. That is another way to figure this out.

[fecmech]

I have as a matter of fact checked the hardness and it's approx BHN 14.

[Defcon-One]

At this point, your guess is as good as mine!

[onesonek]

I have as a matter of fact checked the hardness and it's approx BHN 14.

In what form did you find it in?
But Defcon is right,,,it would be a guess unless you had it analyzed. However, at BHN 14, it sounds shootable to me for any number applications.

[fecmech]

In what form did you find it in?

It was in the form of dive belt weights. I got it from a friend (now past) who worked in some kind of mining machine/repair shop and they made bearings for some of the heavy machinery. Evidently one of the fellows was in to scuba diving and they made the weights for him and I'm guessing out of some of the bearing material.

[mold maker]

Most all the diving weights I have encountered, were made of anything that would melt and pour. I've found quite a few made from lino, WWs, or lead. The rest were a pure mystery.
What you have, alloyed with up to 50% lead should shoot good in any hand gun, except magnum speeds. As is, the 14 BHN is good for even magnum speeds.
Lead is getting to be too precious a resource to waste. If it pours good boolits, keep them separate from known alloy, and shoot them.