Alloy ratio

[BigDaddie]

Hi all,

I got hold of 50kg worth of antimonied lead in ingots from a salvage place today. They are a large business and the fellow indcated that it was 5% antimony and it would hardly mark whe i tried to deform it with my thumbnail. It is real shiny and it was stacked next to some sanded lead ingots that were listed as 99% PB which were real dark.

I'm wondering how to best use this stuff for casting bullets for 8x57mauser & 308win using gas checks. Can u suggest a good alloy using this stuff? I can get old of lead sheets so I really need to know a ratio that would work for my application.

I'm completely new to this so I want to start off on the right foot.

Thanks in advance,

BD

[carpetman]

Big Daadie-Welcome. Over 40 years ago when I was contemplating starting both reloading and casting I was reading the Lyman manual. It gave detail of exacting amounts of whatever to add to wheelweights to come up with an exact blend. In my pea brain mind,my question was how could that be? I figured--maybe false figuring that wheelweights were made of whatever they could find that would melt. So if you really had an unknown as the bulk of the mixture,how was a little bit of exact going to make the whole thing exact? So I used wheelweights and whatever and it seemed to work for me. Then I started reading with .22 cal you need tin to get good fillout. I bought some tin and didn't get fill out--got cave in--my wallet had a cavity it didnt previously have,and there was no room for a cavity. Try that stuff you have and it will probably work fine as is.

[grouch]

I find that my bullet weight is more consistent if I add 1 - 2% tin, possibly due to better fill out. If you plan to water drop or heat treat your bullets to make them hard, the tin content can't exceed the antimony.

If you use your metal as is, you probably need to cast at fairly high temp. to get decent results.

[BigDaddie]

So add in some pure lead to bring the casting temp down then?
Tin makes the alloy flow better?

I have the lee and Lyman manuals on the way which will help answer some of my greenhorn questions. Thanks for your patience guys!

[hunter64]

I wrote up a cheap and easy way to test lead hardness a few month's back and it works great, I don't know how to post the link but do a search with my handle hunter64 and search for "Cheap way to test lead cast hardness" . You need pure lead about 5 lbs will be plenty and a big steel ball bearing. Once you find out the relative BHN number at least you will have some sourt of idea on what it is mixed at. You might have lino, or harder and it would be a waist to use it as is if you could mixe it 10 to 1 or 5 to 1 or what have you.

[Ricochet]

Well, adding in pure lead brings UP the melting point. The more it's alloyed, the lower the melting generally. But you may have to cast hotter to get the boolits to fill out well.

If you want hard boolits, try casting with what you have and water dropping before you try changing the mixture. It may work just fine. But if you can get soft lead sheet cheaply, what I'd personally use for most things is about 1-2% antimony, with or without a bit of tin, water quenched. Comes out pretty hard that way after it ages a few days, and it's nice and malleable.

[NVcurmudgeon]

Big Daddie, if the place where you bought the alloy is trustworthy, and they do sound like they are a cut above "Bubba's Junkyard," I would be inclined to go along with what they said. If you weigh an ingot, and figure out how much 1/20 th is, and add 1/20 th tin, you would have homemade Lyman No. 2 metal. This is the alloy that LYman recommends for just about any cast bullet purpose. According to Lyman's Cast Bullet Handbook, antimony will not alloy with lead. Instead it will become pure antimony crystals surrounded by pure lead crystals, and lead your barrel to beat the band. To get antimony to alloy with lead, you need to add tin. The three metals together will make a homogenous alloy. The easiest to get source of tin, if your metal yard doesn't have any, is lead-free solder from a hardware or plumbing supply store.

[Ricochet]

That's not exactly right. Antimony alloys fine with lead, but it crystallizes out as it cools down because it becomes insoluble in cool lead. Tin won't prevent this.

The normal state that antimony in lead assumes as it cools slowly is a fairly coarse structure with relatively large crystals of hard antimony surrounded by a matrix of soft lead. The overall alloy is still soft, because the soft lead around the crystals can "flow" around the crystals and deform relatively easily, even though the crystals do somewhat interrupt the free flow of the lead. Tin in the matrix hardens it up, making the overall mixture stiffer/harder.

Antimony goes into a "solid solution" in lead at elevated temperatures below the melting point of lead. When we water drop boolits to harden them, we want them to still be at such a temperature that it's still in this solid solution. (Water dropping from the mould may give inconsistent hardness if some boolits are allowed to cool to the point that antimony has started to crystallize already.) When they're water dropped in this state, the antimony atoms are more or less evenly distributed throughout the alloy, and the sudden cooling "freezes" it in this state. But now what we have is a supersaturated solid solution. The antimony still will precipitate out over time. But at low temperatures it's much harder for those atoms to diffuse through the matrix to get together and form crystals, so instead of diffusing farther and forming fewer, larger crystals (the way they do when slowly cooling), they end up forming many more, much smaller crystals that are much closer together. Those hard crystals more effectively "pin" together the slippery layers of lead atoms that slide past each other in plastic deformation, making the overall alloy much harder than the same amount of antimony does when slowly cooled. The same effect happens with a whole bunch of other different alloying metals including arsenic. Tin is an exception, hardening the alloy more when air cooled than when quenched.

There is an excellent article on heat treating lead alloys, from which I'm drawing this stuff from memory, on the "Key to Metals" website. Alas, now they require a paid membership to read their articles, and the files I'd saved thinking I had the article don't work.

[BigDaddie]

Wow! That is great information guys.

So quenching them in H20 (straight from the mould) is the way to lock the antimony in so to speak. What is the difference, metalurgically speaking, heat treating them in the oven?

Is there any merit in getting hold of some bar solder to use with the metals I have already? That is if I do not need it to be any harder and it fills/pours well?

Thanks,

BD

[imashooter2]

What is the difference, metalurgically speaking, heat treating them in the oven?


Consistency of the result.

[454PB]

Tin adds fluidity, and very little hardness. If you are going to quench the boolits and size them, they need to be sized within hours or they will resoften. Heat treating is more consistent, but again, the boolits need to be sized first.

[BigDaddie]

So if u dont quench the boolits in H20, do u just drop em onto a wet towel, let them cool, size them and then heat treat em in the oven?

Is there a need to size them quickly using this method due to avoid the softening?...or is that problem a result of H20 quenching only?

[Ricochet]

If you air cool them they'll be soft enough for easy sizing. If you size them right after water dropping they are, too. Wait an hour or two and it starts getting pretty tight.

I have trouble dropping them on a towel for air cooling without damaging the hot, soft boolits. Water dropping's easier to keep the boolits in good shape.

[NVcurmudgeon]

Big Daddie, please post what you did with your alloy, and how it came out.

[BigDaddie]

I sure will. I am still waiting on my moulds to come so it may be a while. I spent a few hours yesterday smelting down some lead sheet scrap I found into the muffin tray moulds. I have 16 shinny muffins in my shed now along with 2, 2' ingots of the antimonied pb. I cant wait!