at what point does antimony have no effect on hardness

[40-82 hiker]

Just trying to get a handle on this:

This is probably a ridiculous question, but at what point does antimony no longer have an effect on an alloy (in this case 20:1)? Specifically, would 0.15 percent antimony make any difference at all? That is 33 times less antimony than is in Lyman #2. Other than just trying it, I'm looking for some experienced opinions.

Thanks.

[el34]

Here's a handy equation-

Brinell* =* 5 + ( 0.29 * Tin ) + ( 0.92 * Antimony* )

Pure lead is 5BHN. Tin and antimony make it harder. I doubt adding 0.15% would be measurable.

I found this-

The Brinell hardness of cast antimony is 325–340

[shadowcaster]

I don't know if it will make a difference or not. Try it and see.

el34 - Pure lead is 5BHN. Tin and antimony make it harder. I doubt adding 0.15% would be measurable.

Tin actually does very little in the hardening department. It adds toughness and is more for helping to bind the antimony and lead making a smoother flowing alloy resulting in clean, crisp edges, and better fill out.

Shad

[bangerjim]

Pure antimony is very hard and waaaaaay out of your melting temp ranges with our standard pots.

If you want to mess with adding it to your mix, check out the different alloys at rotometals. They have done all the tricky alloy magic for you.

bangerjim

[40-82 hiker]

Here's a handy equation-

Brinell* =* 5 + ( 0.29 * Tin ) + ( 0.92 * Antimony* )

Pure lead is 5BHN. Tin and antimony make it harder. I doubt adding 0.15% would be measurable.

I found this-

The Brinell hardness of cast antimony is 325–340

Thanks to all. It looks like this is a nothing. This formula helps. There are different forms of hardness, though, and I guess I was wondering if the antimony would change the nature of the 20:1 in a way harmful to the benefits of 20:1 regarding obturation. Looking at the results of this formula, however, and the consensus of responses, this little bit of antimony cannot have any harmful affects.

[Defcon-One]

The real answer is at ZERO %. Anything over that is going to have an effect. As one person stated, "it may not be measurable" but it will be there.

Antimony works against a binary (Lead/Tin) alloys main benefits, obturation and expansion, so adding some Antimony will introduce a bit of brittleness or some resisitance to deformation. The more you add, the more effect it will have. It is probably not good for an expanding bullet, especially as velocities go higher. Sorry to say, I do not know exactly where that threshold is!

I use 25:1 in my hollow point handgun loads with very good results and no weight loss after expansion. In 38 special, I can get expansion from .357" out to .605" with no loss in bullet weight. Just the nice clean classic "mushroom".

I'd do some testing at 0.25%, 0.50% and 1% Antimony and see how they work! That will probably be a fun experiment and then you'll know for sure and have a good insight to how and where the critical changes occur.

[BubbaJon]

I wish I was at my desk - there is an excellent writeup on the metallurgy on one of the cast sites. If memory serves me correctly teh tin acts as a "cage" around the antimony up to 2x. So if you have 2% tin then it will "contain" up to 4% antimony. Anything over that the antimony causes shear patterns which can cause teh boolit to shatter or shear along something akin to a fault line.
I've always been told 2% tin is max.
Also on here somewhere is a spreadsheet where you can play with percentages to your hearts content and see what the mix would end up as. It is an EXCELLENT resource as it allows you to mix different common items like ww, sinkers, 50/50 plumbers solder etc.
I used it to cypher how much linotype to add to my ww.

[popper]

Tin & antimony tend to form like stalactites in a cave. Not good, as tin will be soft & antimony hard. The more antimony the worse the problem. Tin does mix with the antimony as stated, but will grow fingers after time. Grain refiners like sulfur, copper, silver, arsenic will make small particles of antimony which is good. Water dropping, quenching, heat treating, whatever you want to call it 'freeze' the small pieces so they don't form the long finger structures. To answer the original question, <1% will have no noticeable effect on lead. Sb is found in Pb ore so there probably will always be some miniscule % of lots of other metals. Like Ivory, 100% is very expensive.