Tin ?

[6mm250]

Does tin harden the alloy at all or is it just for good mold fill out ?

Thanks

Mike

[montana_charlie]

When added to pure lead it will harden it up to a point. If you get as high as 10-1, no more hardening will occur, and your bullets will be pretty low on weight.
When tin is used in antimonal alloy, the antimony has a much greater hardening effect than the tin.

An alloy with more tin than antimony will change hardness, cycling up and down, over time.
When tin content equals antimony, the alloy hardness is very stable after an initial increase in hardness after casting. A test run by Dan Theodor showed alloys of this type remain quite stable over a two-year test period.

He recently posted this graph which was plotted from his findings.

http://i684.photobucket.com/albums/vv203/montana_charlie/Graphof4AlloysBHNOverTime-1.jpg

CM

[Larry Gibson]

montana charlie is orrect if you are adding tin to pure lead. However, you mentioned "alloy". If tin (2%) is added to COWWs it makes the antimony mix better in solution with the lead and a harder and better alloy is the result.....along with a lot better mould fill out.

The article in Lymans #3 & 4 CBH explains it all in the technical veracular. However, in an alloy where there is already sufficient tin adding more will not make the alloy harder as only so much tin/antimony can mix in solution with the lead. The articles explain all that.

Larry Gibson

[lwknight]

The problem with using tin as a hardener is that eventually it will soften.
I had some old tin/lead bullets that were as soft as pure. Once I melted them down and re-cast they were hard again. I think it takes a few years to fully age soften but it is a fact.

[fredj338]

I think tin toughens the bullet more than hardens it. For higher BHN, you need antimony, but that makes a bullet more brittle too.