Metal density

[d_striker]

Out of lead, tin, and antimony, which is the most dense?

I've got some 124 grain molds on the way and was thinking how alloy composition affects the final boolit weight.

I would like to go heavier than 124 grains rather than lighter.

[Tom Herman]

Hi Striker,

Lead has a density of 11.35 compared to water.
Antimony is next at 6.691.
Tin brings up the rear at 5.75.
You're probably not going to use more than a few percent of Antimony or Tin, so expect your weight not to go down very much.
With molds, it's not the weight that matters (plus or minus a bit), it's the consistency that's important.
People panic because a mold may drop a few grains either way. It's not a big deal.

Happy Shootin'! -Tom

[randyrat]

Use 50%lead and 50% WWs and you may drop a 130 or more boolit. If 50/50 is too soft for your load Water Drop them for harder boolits.
Straight WWs you'll drop heavier than 124 gr anyway.

[randyrat]

I thought about your question a little more and here is a good way to help you make consistant boolits(cast).
Fill your final casting pot about .75% up (25% fudge room). Get everything up to temp and start casting. Don't measure your first 10 boolits throw them back. I don't save any boolits untill everthing is dropping real good out of my mold. Then i know the temp is right.
Now, weigh your boolits...Lets say you dropped a 195 gr boolit out of a 200 gr mold and your target weight for that boolit is 205 gr, add some soft lead,get everything up to temp again and recheck weight. Do this until you hit your target weight. The other way- lighter boolit add Tin or lynotype
I use this method to get consistant boolits from different casting sessions.

[Tom Myers]

Hi Striker,

Lead has a density of 11.35 compared to water.
Antimony is next at 6.691.
Tin brings up the rear at 5.75.
You're probably not going to use more than a few percent of Antimony or Tin, so expect your weight not to go down very much.
With molds, it's not the weight that matters (plus or minus a bit), it's the consistency that's important.
People panic because a mold may drop a few grains either way. It's not a big deal.

Happy Shootin'! -Tom

Hi Tom,

You might want to re-check your source.

I believe that these numbers might be a tad closer:

Specific Gravities:

Lead = 11.345
Tin = 7.337
Antimony = 6.70

When calculating the specific gravity of an alloy, one must use the reciprocal of these values. That is to say, divide the ratio of each metal by it's specific gravity, add them up and then divide the total into 1.

A nominal Wheel weight metal alloy is composed of 95% Lead, 4.5% Antimony and 0.5% tin.

Divide each percentage by 100 to get the ratio of each metal:

Lead = 0.95
Antimony = 0.045
Tin = 0.005

Then

0.95 / 11.345 + 0.045 / 6.70 + 0.005 / 7.337 = 0.91135225

1 / 0.91135225 = 10.972705 = The specific gravity of nominal wheel weight alloy.

Hope this helps.
Tom Myers
Precision Ballistics and Records (http://www.tmtpages.com)

[wmitty]

tom

thank you very much for this information! I have been looking for this formula for a long time!

[Tom Herman]

Hi Tom!

Thanks for the correction! I appreciate you catching the error with the Tin. There was apoparently a misprint in one section of the Handbook of Chemistry and Physics.
I checcked a different section and found the correct density.
I'm mortified that I put the wrong figure out, but thankful that you caught it.

Happy Shootin'! -Tom



Hi Tom,

You might want to re-check your source.

I believe that these numbers might be a tad closer:

Specific Gravities:

Lead = 11.345
Tin = 7.337
Antimony = 6.70

When calculating the specific gravity of an alloy, one must use the reciprocal of these values. That is to say, divide the ratio of each metal by it's specific gravity, add them up and then divide the total into 1.

A nominal Wheel weight metal alloy is composed of 95% Lead, 4.5% Antimony and 0.5% tin.

Divide each percentage by 100 to get the ratio of each metal:

Lead = 0.95
Antimony = 0.045
Tin = 0.005

Then

0.95 / 11.345 + 0.045 / 6.70 + 0.005 / 7.337 = 0.91135225

1 / 0.91135225 = 10.972705 = The specific gravity of nominal wheel weight alloy.

Hope this helps.
Tom Myers
Precision Ballistics and Records (http://www.tmtpages.com)

[Firebird]

Uhh, there is NO guarantee that averaging out the densities of the component metals will give the correct density of the resulting alloy. Antimony affects the crystalline structure (much more so than tin) and this affects the density of the alloy much more than simply being a less dense metal. Antimony and Tin also form what is known as an "inter-metallic compound" (the antimony and tin atoms pair up together until one of the metals is all used up) when present together in a lead alloy, and this also affects the resulting crystalline structure and density.
The "average density" calculated may be close, but it won't be exactly correct. Water and ice are made of the same molecules, it's the different arrangement of the molecules that causes ice to have only 90% of the density of water.