Lead Free Alloy

[bradsoto]

Hello and thanks for the wealth of information. This is my first post.

I wanted a lead-free casting alloy to get around some laws here in Canada. Of course I started with bismuth-tin, and ended up nowhere. The problems with bismuth-tin are (among others):

• low melting point (cant powder coat, lots of fouling)
• expansive (sticks in the mold, frustrating as hell)

So I needed to find an alloy that contracts with a higher melting point than bismuth. I alloyed bismuth with zinc. Around 10-16% zinc is the sweet spot, you dont have to bang your mold all day at 10% (minimal expansion) and 16% is the isostatic (no expansion or contraction) eutectic.



Here is what they look like cast. The larger bullet is 210 grains and the smaller is 105. I designed a subsonic bullet shape over at Accurate Molds (this was my first design for tumble lubing bismuth-tin boolits)

http://www.accuratemolds.com/bullet_...=31-252S-D.png
http://www.accuratemolds.com/bullet_...=31-126S-D.png



It's malleable too. Here is a bullet after being chewed on



Next I did the old hammer test. Right away I knew the bullet would be fragmenting



The melt temp of this alloy is higher than powder-coatings. So I coated them and did some test shots. No fouling! Finally I whipped up some ballistic jello in a 4L milk jug to see what would happen with terminal ballistics. The straight through shot is the 210 grain bullet at <mach1 and the perfect expansion shot is the 105 grain at <mach2. This pic is 3D like the old "magic eye" books, just line up the white dots by crossing your eyes and you can see depth.



Where can this go next? I'm making this post because I have to take a break from boolits and I'm hoping someone will take over. To get immediate expansion at subsonic velocities either the meplat has to be bigger, hollow, or we'll have to cut and X down the nose. I already designed a better subsonic bullet with a larger meplat and a 1-caliber long boat tail over at Accurate Molds. The bullet is in the mold upside-down. When the bullet is subsonic the shape of the tail is most important to get right :

http://www.accuratemolds.com/bullet_...=31-242S-D.png
http://www.accuratemolds.com/bullet_...=31-121S-D.png

How fast can this alloy go before we get too much fouling? I don't own a chronograph . Maybe there is another high-contracting, high-temp metal that makes a better alloy with bismuth for cast boolits? I can cast this alloy heavier and cheaper than buying copper bullets... now you can too!

[17nut]

Have you tried pure tin?

[bradsoto]

No. Have you? My first thought is it would melt when you powdercoat it. Maybe it wouldn't need any powdercoating? You could always paper patch... Other than that it seems too light and not stabilize. It's worth a shot once I get back in to casting I'll try it out for sure! I took the bismuth-tin alloy as high as 40% tin.

[dbosman]

There are low temp powder coat materials. Approximately 325° F.
http://www.eastwood.com/hotcoat-powd...p-topcoat.html
http://www.platinum-powder.com/index...owder-coatings

[17nut]

No. Have you? My first thought is it would melt when you powdercoat it. Maybe it wouldn't need any powdercoating? You could always paper patch... Other than that it seems too light and not stabilize. It's worth a shot once I get back in to casting I'll try it out for sure! I took the bismuth-tin alloy as high as 40% tin.

Yes and they shoot fine. Funny golden hue.
I dont need to go lead free as i'm in the old world and we are a tad behind
Tin melts at @450degF is that to close for PC?
https://en.wikipedia.org/wiki/Tin

I use HiTek and it bakes on at @400degF.

The small ones are from a Lee .515-500 mold and the long one is a homemade .50 cal PP mold.

[Guesser]

I came across a supply of modern pewter; 92.5% tin, 6% antimony, 1.5% copper. It makes beautiful light for caliber bullets. Wish I could find another ton of it. As it was I only had about 200 pounds of it, so I use it to alloy lead and get what I want using a Cabin Tree hardness tester and a digital scale.

[17nut]

Pewter is easy to find at yard sales and thrift stores.

It's where i find all my metal for alloying lead

[bradsoto]

Yes and they shoot fine. Funny golden hue.
I dont need to go lead free as i'm in the old world and we are a tad behind
Tin melts at @450degF is that to close for PC?
https://en.wikipedia.org/wiki/Tin

I use HiTek and it bakes on at @400degF.

The small ones are from a Lee .515-500 mold and the long one is a homemade .50 cal PP mold.

Nice I've melted a couple bullets that are closest to the element.

[bradsoto]

I came across a supply of modern pewter; 92.5% tin, 6% antimony, 1.5% copper. It makes beautiful light for caliber bullets. Wish I could find another ton of it. As it was I only had about 200 pounds of it, so I use it to alloy lead and get what I want using a Cabin Tree hardness tester and a digital scale.

This has a higer melt point than pure tin! And a tad bit heavier. Have you ever cast with pure pewter?

[bradsoto]

There are low temp powder coat materials. Approximately 325° F.
http://www.eastwood.com/hotcoat-powd...p-topcoat.html
http://www.platinum-powder.com/index...owder-coatings

Thanks! The Eastwood powder looks to be more what I'm after. I'm using a clear powder from Prismatic Powders at the moment, but it turns the bullets grey like old lead. Have you shot with this powder before?

[runfiverun]

Eastwood makes a good reliable product.

I would try adding some copper to the Bi-Zn mix.
it adds a malleability to the alloy.
we have been working with a Pb-Zn-Sn mix and copper seems to help it out some.

[bradsoto]

Eastwood makes a good reliable product.

I would try adding some copper to the Bi-Zn mix.
it adds a malleability to the alloy.
we have been working with a Pb-Zn-Sn mix and copper seems to help it out some.

There is a bit of copper. I used out-of-circulation Canadian pennies for the zinc

[Peregrine]

Good thread, something else I can tuck away for later. I'm just curious as a fellow Canadian which laws exactly you're having to comply with.

[bradsoto]

Good thread, something else I can tuck away for later. I'm just curious as a fellow Canadian which laws exactly you're having to comply with.

Migratory birds regulations. I said "get around" not "comply 100%" I'm certain a bismuth frangible bullet will reduce any legal risk. Especially at subsonic velocities with minimal report.

http://laws-lois.justice.gc.ca/eng/r...35/page-1.html