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Old February 28, 2011, 08:55 PM   #1
Hog Buster
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What's a little zinc and what does it do?

I see it posted over and over that a just a little zinc mixed in a melt will ruin your alloy. Yet I have never seen anyone post a definitive reason why it does this, or how much is a little.

An inquiring mind would like to know:

Exactly what’s a little?...... An ounce to a pound?...... A drop to a gallon?...... A milliliter to a barrel?

Exactly what does it do to ruin it?...... Make you run higher temps to cast?...... Makes bullets too hard to size?...... Changes the weight?

No speculation, just the facts.
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Old February 28, 2011, 09:42 PM   #2
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Well, cast some boolits with a good alloy. The lead flows into the mold like water. Then cast some polluted with zinc, it's like trying to pour oatmeal into a mold!:barf:

The resulting boolits will have rounded corners, and look like a cheap job of zinc plating on Chinese steel. Also they will be very hard.

A little would be as small as 5% zinc will cause problems, or in other words, 5 zinc wheel weights melted with 100 lead ones. This is a guess on my part, I have never dealt with zinc contaminated lead. Just what I have heard from some others.
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Old February 28, 2011, 09:48 PM   #3
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To me any Zinc is to much,I use a lead thermometer to keep my ingot pot at the right temp to melt lead but not melt any Zinc weight I may have missed during sorting,they float to the top and I skim them off along with the steel clips.

Zinc makes lead alloys kinda thick and mushy,it causes bad mold fillout and bullets cast with Zinc are harder but lighter than the bullet mold would normally produce.

People have and do cast bullet made from Zinc,but both are not a good combination together.
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Old February 28, 2011, 11:03 PM   #4
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Zinc and Calcium (found in modern no-maintenance car batteries), are similar to the affect on bullet casting alloys. The liquid metal fills the mould but as it hardens, it shrinks away from the side of the mould producing misshapen (and unusable), bullets. The exact amount of Zinc and Calcium to produce that effect are unknown. However, if you attempt to dilute the contaminated alloy by adding "good" lead, you will find that you must add so much lead alloy that you will begin to question if you are not throwing good lead after bad before the mould begins to cast usable bullets again. It will only happen to you once before you are damn sure not to get any Zinc or Calcium mixed into your alloy again.
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Old March 1, 2011, 08:18 AM   #5
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zinc percentages ???

Well what`s to say the WW we so carefully sort & watch as they melt don`t already have some % of zinc ?????

I know pure target rifle shooters that cast & desire 2% zinc MAX , but to keep it to a known blend they start with certified alloys or tested blends .

But as they cast , to the naked eye you`ll never notice the zinc is there until you do a bhn test ,then it shows up as a very hard 22-30 bhn bullet !!

I feel snuffy is very close to the answer 5% will start showing up as oatmeal floating about in the melt & start causing problems in driving band fill out !!

My self ,I try to avoid it as much as possible as I`ve dealt with a batch before !!! NO FUN

But it was before the time I now spend on the forums & did`nt know exactly what it was so I let it float to the top & dipped most out (almost 1/2 the pot of melt I had) & did manage to get plinkers from the rest of the pot , but not nice looking bullets to say the least , but very hard & absolutely no scratching with the thumbnail !!!!

But in these days I`m afraid useable cheap alloys are qwikly becoming a thing of the past !!!
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Old March 1, 2011, 02:32 PM   #6
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Never heard of someone intentionally including zinc before. I've always heard the problem was it raised surface tension, but this thread on how to make solder suggests another mechanism. It states that 1.6% is the maximum amount of zinc that will alloy with lead. Any more than that just is part of a molten mixture, and the mixed but not alloyed zinc, having a higher melting point, will tend to harden first during cooling, interfering with where the lead can flow.

That article describes using sulfur to flux zinc out, but that's done before adding tin. This thread at the castboolits forum describes doing sulfur fluxing to clean zinc out of metal, but I don't know how much tin and antimony it removes. Whole process sounds hazardous and pungent.
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Old March 1, 2011, 06:51 PM   #7
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UncleNick,

Once again you have offered a post with some very usable information. Thanks. I have yet to encounter any Zinc in my pot but at least not all is lost if I do. I do agree it sounds easier to keep it out then to to deal with it after the fact.
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Old March 2, 2011, 09:42 PM   #8
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Well in the past I’ve read the piece from “Practical Up To Date Plumbing”. Seems that it has the only answer for removing zinc from solder alloy. Too bad there’s no newer information, the book was written in 1914. It’s still good information as bullet alloy is very close to soldering alloy. Still not too many definitive answers on problem zinc in bullet alloy.

Bad castings are always a source of wonder. I wonder if it’s the scrap, the temperature, the mold, phase of the moon, what? Many times too many variables to ever pinpoint the problem. Ah... the magic of casting, keeps us coming back for more.

Of course there’s no limit as to what you may find in scrap. Take wheel weights, after all they’re not made to any exacting specifications I’m sure. I can remember many years back when it was a on-no to use anything with much antimony in it for making bullets. Over the years that’s gone by the way side. Now a bit of antimony is seen as good for bullets. Lord knows what else may lurking in them to give you problems.

Speaking about antimony, I’m not sure how much is in today's wheel weights. Along with tin I would guess that because of cost, as opposed to lead, there’s very little in them. Only the barest amount necessary I’m sure.

Most wheel weight is tin starved for bullet making. A shot of 50/50 solder works wonders for helping the bullet alloy fill the mold. On the other hand 50/50 solder is getting expensive and hard to find. Most solders used for plumbing are 95/5 tin to lead. Of course this will work in your bullet alloy, just different amounts to the mix. Linotype was always an alternative, but is just about a thing of the past. I sure made some pretty shiny bullets with it though. It cast light and was hard, a PIA to size.

I’m sure that sometime or another I’ve cast bullets with some zinc in them. It must have been less than 2% because they had no noticeable differences from many others I cast out of questionable alloy. Like antimony, in small amounts it may be even be beneficial, time will tell.

So far I’m not having any trouble with Zinc wheel weights. The last several hundred pounds I obtained only had 6 or 8 individual zinc ones along with about a pound or two of iron ones. However while melting this batch I noticed that it was somewhat tin starved, so adding a bit will be necessary.

In the future I guess that we’ll be using zinc........ Hey, it can be done, has been done and works without leading, but for the foreseeable future I’m scrounging lead wheel weights.
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Old March 3, 2011, 10:46 AM   #9
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What I've read is that wheel weights used to be about 4.5% antimony (Lyman handbook) but that now a lot of them are 3%. Tin was never over 0.5%, and you need about 2% to make the good fill and flow temperature range more forgiving, IME.

As far as too much antimony goes, Veral Smith wrote that he used to think wheel weights were a universal bullet metal until he moved to Idaho and discovered that in extremely cold weather, wheel weights would shatter on bone. That's due to antimony content. I don't have an exact "good" number for you, but 2% tin and 2% antimony would be where I would start investigating if I had to run hardened bullets in -20°F. Adding a small amount of silver will help harden alloy, too, so some substitution might be involved in making hard "low antimony" bullets for all conditions.

High antimony content alloy, such as linotype, is often used in bullets, but not usually for hunting so much as for target shooting. There again, I'm pretty sure breaking up is the issue in tissue, whereas paper holes are punched with it just fine.
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Old March 3, 2011, 08:08 PM   #10
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Yeah, I was thinking back to my bullseye days. Hard bullets are like full jacketed on game. Plenty of penetration, sometimes right on through.

I agree that there’s very little tin in wheel weight. I don’t think my last batch contained even 0.5%. I’ve also got doubts that there’s 3 % antimony in them. I remember years back they generally had a much duller finish than those I cast today. I feel that the percentages of lead, tin and antimony has changed over the years.

I picked up another 100 pounds of wheel weight today and had a short conversation with my friend the tire store owner, an avid shooter, but not a reloader. He said that he is seeing less of the zinc ones and more of the iron ones. Maybe production costs are changing and iron is cheaper. That would be nice.

As for hunting bullets wheel weight is not the best alloy. If you want penetration it’s fine. In fact it can be shot through 1/4 inch mild steel with just about any rifle load. Quench it and you’ve damn near got armor piercing.

For hunting I used an alloy of 15 parts lead to 1 part tin. In solid bullets it stayed together and mushroomed just a bit. With hollow points it was devastating. However it took a few tries to figure what velocity worked best.

Most of my hunting was done in California or here in the south, so I never encountered really cold weather. I did encounter a bit during cold weather training in the U.S.M.C. at Pickle Meadows, California. It was so cold there that everything froze, even oil and grease. Didn’t do any hunting there, too busy looking for a warm spot.

Another thing comes to mind concerning antimony. I remember reading somewhere that antimony shrinks on cooling. If a fact, another reason for keeping the content low in bullet alloy.

A few years back silver was almost cheap enough to consider its use as an alloy, but not today, except maybe for the Lone Ranger.

I’ve given some thought to casting bullets out of other alloys, brass, copper, etc. So far it’s only been in my thought processes. Generally after I take a nap it goes away. I guess that the search for the magic bullet doesn’t consume me as much as it did at one time.
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Old March 4, 2011, 11:53 AM   #11
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Elmer Keith went from 20:1 to 16:1 lead:tin in developing the .44 Magnum, so you seem to have rediscovered what he considered the best mix.

I was remembering wrong: the silver in casting alloy wasn't for hardness, but for better mold fill. I think Veral Smith was talking about an amount so small he was just adding a few inches of silver-bearing soft solder to a 20 lb pot. Must reduce surface tension. Laser Cast bullets have some silver in them according to their site literature.

The Lyman Handbook has shrinkage for some alloys. No matter what the constituents do by themselves, once in an alloy their effect can differ. I also remembered Lyman's wheel weight numbers wrong by 1/2 a percent. They list it as 95.5:4.0:0.5 lead:antimony:tin. So, 4.0% antimony. The LASC site had something on the changes in wheel weight alloys over time, which apparently are regional. Mostly they are cast using recovered scrap as a primary constituent, so purity and consistency was never part of the picture unless you purchased virgin alloy.

Based in the above, Lyman shows the as-cast diameters for a 0.458" mold of theirs would be:

0.4575" lead
0.4583" wheelweights
0.4590" Lyman #2 alloy (90:5:5 lead:antimony:tin).

So, at least in the alloy, the antimony is not causing a shrinking problem, but rather seems to do the opposite. The WW and #2 alloy melting points are lower than for pure lead, so the mold itself would be slightly smaller, yet the bullets come out bigger.

As to copper, I see no problem with it except maybe for hollow points. The original Babbitt (named after its inventor, Isaac Babbitt, I learned; hence the capitalization) formulation apparently had copper in it to make it harder and more durable than lead and tin and antimony alone, though nobody knows the exact original formula. Now there are a number of both lead and tin based Babbitts, but they all cast well and precisely to make journal bearings. A fellow on another board got a big supply of scrap Babbitt at one point that he said made wonderful non-expanding wide meplat bullets that survived impact well, but I don't know what temperatures he was shooting in or how heavy the bones he hit were. Given that Babbitt has seen use in engine journals, I don't expect it is too brittle in the cold. Have to be tried, though.
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Last edited by Unclenick; March 4, 2011 at 12:06 PM. Reason: typo fix
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Old March 6, 2011, 12:40 PM   #12
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Silver solder? I hadn’t thought of that. I’ve got a few rolls around here, I’ll have to give it a try.

I’ve often thought of using Babbit, but haven’t had the opportunity.

Copper and brass should work OK, just that casting temperatures might be a bit high. I think gravity casting would be out of the question for these, even heavily alloyed. Centrifugal or vacuum investment casting might work, but the end might not justify the means. Spin casting is probably out as the alloy temperature would probably exceed the vulcanized molds working temperature.

A bit more food for thought.......
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Old May 21, 2011, 04:14 PM   #13
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There are various contaminants that make lead uncastable or to least difficult to cast. Zinc is one of them. It has the effect of creating a skin on the surface of the lead. I is usually not easy to see, but I have observed it inhibiting the easy stream of alloy at the pouring spout. It results in poor quality bullets because it prevents proper mould fillout, rounded corners and the like. 0.20% is enough. Yes, that's one quarter percent.

There is no way of removing it, but there is an easy remedy. Cast it into ingots and mix it not more than 10% with good alloy. Unless you have an unusually high percentge, that will usually water it down to a concentrtion too small to do any harm.
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Old August 29, 2013, 04:51 PM   #14
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re: zinc in lead

I got my WW mix too hot one time and melted the zinc with the lead. I got it to cast the bullets ok. Heck, they even grouped ok. But I spent a lot of time and money making a deceleration bullet trap so I could reclaim my lead and I can tell you, when they hit that steel, they turn to dust. Makes you wonder what would happen if you used them on game.

I read somewhere that a person might be able to remove the zinc by getting the lead up to it's melting point and the zinc below it's melting point then fluxing it with sulfur. I don't know if this will work but if I try it it'll damn sure be outside with a fan blowing the fumes away from me..BTW the last bunch of WWs had more zinc in them that lead, I gotta find another source.

I know this ins an old thread but I believe getting the info out there is just as important as corresponding with other members on the board.
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Old August 30, 2013, 06:44 AM   #15
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I agree with your last sentiment.

Do you have any idea what portion of your alloy was zinc?
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