Lead-free bullet casting alloy

Ian

Notorious member
I want to continue the "Condor Cuddler" thread here but more to the point of attempting to find a lead-free substitute for cast bullets rather than resorting to the usual Barnes et alia solution for hunting in areas which no longer permit the use of lead bullets.

As mentioned on the other thread I discovered a technical article which explored the addition of ternary additives to bismuth/tin for the purpose of altering the grain structure for increased ductility. Small additions of antimony to eutectic 57/43 bismith solder showed a dramatic reduction in grain size and equally dramatic increase in ductility. My hope is that a similar ductility increase can be achieved with an 88/12 alloy (more suitable to making bullets) with the small antimony addition. This should be the case because the precipitation mechanism of ductility is primarily a function of Sb/Sn intermetallic forming along the bismuth lattices and this should occur at least to some extent independently of specific tin or bismuth concentrations.

I contacted Rotometals to forward a copy of the article and the interest of their production staff was piqued sufficiently that they prepared some sample alloy for me to test. I should be receiving this alloy in the coming week.

First order of business with the new metal will be figuring out how to cast a bullet with it, then on to the physical testing and if all that looks promising enough, then on to some shooting tests. Stay tuned.
 
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Brad

Administrator
Staff member
This will be an interesting test to follow.
This is truly pushing the envelope on bullet casting. To see how it casts, handles pressure and velocity, does it size well, and terminal performance.
 
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JonB

Halcyon member
Ian, that sounds like something I need to follow.
Sadly it's only a matter of time for Minnesota...we always follow close to CA.

I've attached a recent article from the State's newspaper.
Disclaimer: I realize this is borderline politics, I will not discuss any politics or anything about this article, I'm just posting this as evidence that it'll likely happen in MN, sooner or later. If it needs to be deleted, so be it.
 

Brad

Administrator
Staff member
As long as we keep the politics out of it I don’t mind.
If Ian, with help from Rotometals, can find a lead free, castable, workable alloy then I am all for it.
 
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CZ93X62

Official forum enigma
Specific to my state--CA--the Fish & Game Code requires an "expanding tip" for big game hunting--black bear, deer, tule elk, pronghorn. No such requirements exist for non-game or small game species. Game birds are shotgun-only, #2 birdshot is as large as can be used. My interests are focused primarily on small game/non-game hunting, but if a large game bullet can be derived THAT WOULD BE AWESOME.
 
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Ian

Notorious member
If anyone lurking out there has experience casting bullets with the 88%Bi/12%Sn alloy, input would be appreciated. From reading other BB posts I gather that this alloy expands as it cools, tends to stick in the moulds, requires only about 500⁰F to cast, and pretty much shatters like glass. Rotometals added .75% antimony to three bars of their 88/12 and that should increase ductility a great deal as well as raise the melting point slightly and possibly increase the toughness. Still, it appears that casting bullets, particularly hollow point ones, is going to be a challenge.

Any input to the specific properties a lead-free hunting bullet needs to meet law is welcome, paraphrase if necessary to avoid blood-pressure spikes but legal facts are needed if we're to find a solution to the imposed restrictions. I get it that people are very angry and the legislation is often made on false premises, but "it is what it is" so please support the effort to deal with it and carry on. A good example of information needed is I understand that CA law requires some sort of expanding property so the bullets must be soft enough to mushroom or malleable enough to make an expanding hollow-point design. I don't know if this alloy I'm going to test will be malleable enough but we'll see.
 

Ian

Notorious member
Thanks for the clarification, Allen, I missed your last post before submitting mine.
 

CZ93X62

Official forum enigma
My focus is not on the politics of this question--it is upon the adaptation of hobby interest to follow the laws as written at the same time we pursue the underlying goal of not being dependent upon commercial vendors for our projectiles. If that can be done relatively simply and without a lot of gymnastics and booshwah, then I am on board.
 
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Brad

Administrator
Staff member
Expands on cooling could make dropping from mould “interesting”. Bigger issue possibly is further growth after cooling.

If anyone can find a way to make this work it will be Ian. I can hear the wheels spinning in his head from here.
 

Walks

Active Member
I thought CA DF&G had a Specific listing on what Commercial Brands of ammo & bullets were allowed. And only those listed were legal.
 

Ian

Notorious member
My focus is not on the politics of this question--it is upon the adaptation of hobby interest to follow the laws as written at the same time we pursue the underlying goal of not being dependent upon commercial vendors for our projectiles. If that can be done relatively simply and without a lot of gymnastics and booshwah, then I am on board.
My goal in a nutshell
Expands on cooling could make dropping from mould “interesting”. Bigger issue possibly is further growth after cooling.

If anyone can find a way to make this work it will be Ian. I can hear the wheels spinning in his head from here.
Rotometals reported 19-ish bhn frombthe 88/12 alloy but that it was inconsistent. That tells me the precipitation-hardening was still taking place at the time the tests were conducted because we see the same erratic numbers with low-Sb lead alloy until it stabilizes. We need to really understand the properties of this alloy and maybe make some more tweaks to get it right. Shallow-groove moulds will likely be the norm and some mould materials will likely prove better than others.
 

fiver

Well-Known Member
so far what I'm seeing is the antimony is going to act like copper would in a Sb-Pb alloy.
I still can't help but feel something else is going to be needed to smooth things out so the alloy can flow under stress.
 

fiver

Well-Known Member
also another idea.
why not paper patch or powder coat a very shallow groove Lee style core.
minimal steep angled grooves.
 

Ian

Notorious member
Definitely planning to try Lee t/l bullets and PC, but not first because PC isn't totally mainstream yet.
 

Brad

Administrator
Staff member
With the low melt point of the alloy and the needed temp for cure of PC is slump a concern?
 

Ian

Notorious member
We'll see. The 88/12 melts at about 495⁰F but I don't have any idea what kind of slush phase it has.

Edit: 11/26/19, I just realized me remembering a 495⁰F melt point (from Rotometals) is totally wrong, they said it was 395. That would explain the slumping I got when coating at 385 in the oven and little beads sweating out at 340.
 
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Brad

Administrator
Staff member
How many pages is your preliminary testing protocol? I have a feeling there is something in writing well beyond a single page.
 

Ian

Notorious member
Heheh....well, you know me.

However, job #1 is make a bullet and record temperatures and casting characteristics, check it for hardness and diameter right away and at intervals, and hit it with a hammer. Mainly the hammer test will tell us what we need to know most.