Lead-Bismuth-Copper

[justindad]

I don’t like paying $30+ per pound for tin. For me, copper wire is basically free. From what I’ve read, adding copper raises the melting temperature beyond what I want to deal with. Now I’m wondering if bismuth ($10/lb) would be a good way to reduce the melting temperature of a lead alloy with copper.
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Does bismuth make lead brittle like antimony, or ductile like tin? If that would make a brittle alloy, then I’m not interested. It’s in cerrosafe, so I’m hoping for ductility.

[unclemikeinct]

J's dad we have to slow your roll there. one pound of tin is only enough material to get you 2% in a fifty-pound load of Lead. Good enough for most rifle bullets. Half that amount for more modest pistol velocities. Tin is nice for helping fill out the mold. Use only as much as you need. Myself I use Pewter scrap I find in thrift stores & tag sales. Bismuth I just Don't know , never heard or considered it in my alloys/molds. Tell us about the lead scrap you are starting with. and what you will be casting for Rifle or Pistol. The hard to find ingredient is Antimony. 4% or slightly more for rifle bullets. About 2% will firm things up enough for most pistol bullet use. You can PM me for pics & more detailed instructions about blending scrap on the cheap. uncle mike

[243winxb]

As cast diameter may be a problem using bismuth? Changes diameter.
Copper plugs my bottom pour spout.

[imashooter2]

This document says bismuth doesn’t harden lead much at all.

https://nvlpubs.nist.gov/nistpubs/jres/5/jresv5n5p1085_A2b.pdf

You should have no problem getting pewter or solder at considerably less than $30 a pound for the tin. There have been several ads here over the last month.

[justindad]

As cast diameter may be a problem using bismuth? Changes diameter.
Copper plugs my bottom pour spout.

How much copper were you using when the spout got plugged?

[Sasquatch-1]

I use range scrap lead for handgun bullets. I only add tin when there is a problem with mold fill-out. I do not shoot rifles at a thousand yards and the accuracy of what I use is better than the accuracy of these old hands. I also find my tin at yard sales and thrift stores and have enough to last the rest of my life. So, look at other sources for tin and you might be surprised at how cheaply it can be obtained. Also, there are several good threads here about identifying pewter.

[unclemikeinct]

Man I miss the old days. Wheel weights were free [made from lead & antimony] & made really good bullets. Add some 50/50 tin lead solder & you had rifle bullets. Today every batch has to be blended/fluxed, cast into ingots, tested then labeled for use.

[popper]

There is a thread of casting Rotometal Pb/Bi in 223. Very light weight compared to Pb and very hard. Very difficult to cast. OP recover some bullets, no deformation. Cu wouldn't be needed.

[Rickf1985]

I have seen a couple of threads now where you seem to be looking for much harder bullets using copper. Have you ever thought about casting bullets from zinc? Lighter but VERY hard.

[justindad]

Not looking for anything very hard… just something tough without much tin. Why? because I like overcoming challenges in order to be a cheap-skate.

[bangerjim]

I have a ton (literally) of an alloy that the aerospace industry uses to hold turbine blades while machining them:

Pb 27
Bi 55.5
Sn 12.4
Sb 4.4
(verified by x-ray gun shoot)


Melts @148°F a very nice alloy for a lot of stuff in the casting arena (non-gun related). Just 1oz of that added to 3# of pure Pb gives a hardness in the 11-12 range, so there IS magic in eutectic alloys!

No Cd so it is very safe to play with. I use it for reproducing missing cast /molded trim on antiques. A mold of the original piece can be made of hobby rubber or casting clay from Hobby Lobby, since the stuff melts at such a low temp. Many of the "ingots" of this stuff were poured into plastic SOLO drinking cups without melting them! The alloy is VERY hard....in the range of 24-26 hardness. Perfet for trim castings. And does NOT rub off on your fingers.

It shrinks very little when cold.

But your best way to add significant hardness to your mix is adding a pre-mixed Sb rich alloy. I have one that is 7% Sb and does wonders for increasing the hardness without much Sn. Forget using Sn as a hardening agent. I adds VERY little hardness per percent....you would need to have 25-35% Sb to get anything very hard. I have one alloy that is 55% Sn and it is only ~24 Bhn. Too expensive these days to rely on Sn for much hardness.

And remember Cu adds TOUGHNESS not HARDNESS.

[justindad]

Bangerjim - have you ever mixed that bismuth blend with a standard lead alloy to cast boolits and then do expansion tests?
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My thinking is to add copper for toughness, then add bismuth to knock down the melting temperature. The ultimate hope is to have a tough bullet like a 20:1 lead:tin alloy… without the expense of tin. I see two potential Achille’s Heals: 1) if bismuth makes it brittle, then might as well just use 95:5 Pb:Sb; 2) if adding Cu requires a significant Sn content, then no money is saved.
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If I had to guess at the alloy I am dreaming of, it would be 98.8:0.5:0.5:0.2 Pb:Sn:Bi:Cu.

[Sasquatch-1]

Bangerjim - have you ever mixed that bismuth blend with a standard lead alloy to cast boolits and then do expansion tests?
*
My thinking is to add copper for toughness, then add bismuth to knock down the melting temperature. The ultimate hope is to have a tough bullet like a 20:1 lead:tin alloy… without the expense of tin. I see two potential Achille’s Heals: 1) if bismuth makes it brittle, then might as well just use 95:5 Pb:Sb; 2) if adding Cu requires a significant Sn content, then no money is saved.
*
If I had to guess at the alloy I am dreaming of, it would be 98.8:0.5:0.5:0.2 Pb:Sn:Bi:Cu.



Melts @148°F a very nice alloy for a lot of stuff in the casting arena (non-gun related). Just 1oz of that added to 3# of pure Pb gives a hardness in the 11-12 range, so there IS magic in eutectic alloys!

I would think that with a melting point this low that there would be a severe leading problem with the base of the bullet melting.

bangerjim, I know you said you were not using it for casting but justindad, was asking about something in this area of alloy for bullets.

[dondiego]

They used to make bismuth shot for waterfowl hunting and it was said to be brittle.

[bangerjim]

I would think that with a melting point this low that there would be a severe leading problem with the base of the bullet melting.

bangerjim, I know you said you were not using it for casting but justindad, was asking about something in this area of alloy for bullets.

I would NEVER EVER cast boolits from the straight alloy! It would melt in the barrel.

But multi-alloy eutectic alloys are fascinating as far as the change in melt temp that occurs!

My standard alloy these days is pretty much straight COWW's with maybe 1% Sn added (for certain molds and tough fill-out requirements). Then............. PC everything! :grin: That formula is good for anything I shoot up to and over 2,500 FPS.

Why make something so simple as COWW's (the perfect blend since tires were invented!) into a science/metallurgical nightmare? If you cannot find COWW's anymore, make your own alloy. Easy-peasy.

banger :Fire:

[243winxb]

How much copper were you using when the spout got plugged?

Some kind of babbitt. Unknow % . Was scrap to me.

[Chaparral66]

I have COWW and pewter available if you are interested.