Bullet alloy question

Discussion in 'Ammunition & Reloading' started by DLS, Apr 5, 2018.

  1. DLS

    DLS
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    Hey all,

    I came into a supply of pure antimony and decided to alloy it with some pure lead. I wanted to cast it into 50/50 ratio ingots, to later use to harden wheel weights when I want to cast up rifle bullets.

    The challenge is that antimony melts at 1167 degrees, compared to pure lead's 620 melting point. But once it's alloyed with lead it will melt around 680 or so, well within the normal temp range of bullet casting furnaces.

    So I fired up my casting pot and melted and fluxed (with Marvelux) 3.5 pounds of pure lead. Once melted I added 3.5 pounds of small chunks of antimony. To help it melt (since my casting pot maxes at 700 degrees) I held a MAPP gas torch on the antimony as it floated on the molten lead. As the antimony melted I stirred and fluxed the melt until the chunks were all melted.

    If you are still with me ... a couple of questions. As I torched the antimony a pretty good head of white smoke was coming off the melt (I had a fan moving air across the pot and away from me). Is this normal? This smoke left a white residue on the edges of the pot. I'm wondering if this is vaporized antimony and if so I should maybe use a lower temp torch, like plain propane?

    Also, the ingots are very grainy and brittle. Perhaps the ratio of antimony still too high? I can leave them as is, but if were to drop one on a concrete floor it would probably shatter. There is also quite a bit of residue left in the pot. It has a gold tinge to it and even when heated to red hot sticks to the side of the pot. It will scrape off the sides of the pot while hot. I've never had any other lead alloys stick like this ... but casting alloys are not 50% antimony.

    I'm wondering if this too is normal. Tomorrow when I have more time I'm going to try and realloy the ingots with and equal amount of lead, bringing the antimony content to 25%. I'm hoping this will clean up the pot and make the ingots act more like normal casting alloys.

    Any ideas or comments about all of this? Thanks in advance.
     
  2. Stomper

    Stomper
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    You wasted a good buzz, man.... you shoulda inhaled that white smoke! :D;)
     
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  3. DLS

    DLS
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    Yeah, toxic fumes ... my wife might agree with you since insurance money would be nice!

    LOL
     
  4. jordanka16

    jordanka16
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    50% antimony is way high for a bullet alloy, that's why they're grainy and brittle. Normal bullet alloys have like 5% max, usually closer to 2.5%.

    They're probably fine as is, but I would make small ingots, since you will need very small amounts to harden alloy.

    You should also acquire some tin to mix in to the final alloy of it doesn't have any, it will fill out molds better.
     
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  5. DLS

    DLS
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    I have a supply of pure tin and will use that in the final mixture for the particular bullets I'm casting.

    The 50/50 mix is just to alloy the antimony enough to get it to where it will melt in my bottom pour electric furnace without resorting to a torch (and the potentially toxic smoke).

    It will then be used to make up various alloys, such as Linotype (12% antimony) or Lyman #2 (5% antimony).

    I have never messed with pure antimony before. I've always had a supply of Linotype or Monotype to use in adjusting the final mix. But when you get your hands on a big batch of expensive material for free you got to make use of it right? LOL

    I think I will try to make my mix closer to 25% Antimony and see if that doesn't solve the residue problem. That has got to make the ingots less brittle as well, making for better storage. I'm casting them in 1/2 pound ingots so they break easy as they now are.

    I'm still wondering about the white smoke, can you vaporize antimony with MAPP gas? It took a great deal of torch time to get it to melt so I think no ... but I'm playing in a new sandbox here.

    Any other ideas? Thanks!
     
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  6. Certaindeaf

    Certaindeaf
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  7. Vorpalis

    Vorpalis
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    The white smoke is antimony (III) trioxide, and is reasonably safe, as in if you inhaled WAAAAY more than you possibly could given the exposure you described, and you were a rat, you might have a slightly increased chance of lung cancer.

    The granularity probably has to do with the low temperature you’re able to achieve with your furnace and torch. The molten lead may be eroding and dissolving the solid antimony without actually melting it (think salt dissolving in water at room temp compared to actually melting salt at 1,474 F).

    If you want the über-nerd, Expert Mode explanation, I can oblige :D
     
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  8. DLS

    DLS
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    Thanks Certaindeaf, that was an interesting read. I saw something similar where I got the idea to use a torch since MAPP burns at 3670 degrees , which is three times that of antimony. Propane is supposed to get to 3623 so that should work too.

    This article also had the suggestion of reducing the temperature of the lead melt. That does not seem to make sense to me, but again, I'm playing with a new thing and I remember enough chemistry from school to know strange things happen. Especially considering the addition of Flux to the mix.
     
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  9. DLS

    DLS
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    Thanks for.the knowledge. While I don't have a hood I did set up a good unobstructed air flow both to and from the pot, directed away from me and toward an open door, so I'm pretty sure I was safe enough.

    The article mentioned by Certaindeaf states lower melt temp work better and that submerged antimony will.actually melt into the lead. This doesn't seem right to me, what do you think?

    I understand the tin and antimony never truly melt in lead but form a "mix" much like concrete. How do I get a finer grained mix? Should I be adding tin to the mix? I'm thinking that a lower proportion of antimony will help?

    I would value the information, thanks for.offering!
     
  10. Certaindeaf

    Certaindeaf
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    I hear you. It sound interesting and I'd be interested in any success you might have.
    It sounds like there's a difference between actually melting the antimony as compared to actually incorporating it into the alloy.. many hundreds of degrees I think I saw. I think I saw where one fella can do it at around 600F? anyway.
    What I do know is that vaporized lead fumes are dangerous.. which happens way above its melting point.
     
  11. DLS

    DLS
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    I don't see how a powntemp lead melt (600 degrees) will melt something with almost twice the melting temp ... so call me perplexed.

    I set a fan at near my right elbow blowing across the pot right to left at around 45 degrees. I make sure there are no downwind obstructions and the whole airstream is pointed toward a nearby open door. By Watchung the.smoke.from fluxing it seems this captures all the out gassing and moves it away from me. I hope.I'm right!
     
  12. Vorpalis

    Vorpalis
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    I don't know for certain that what the article and I describe is what's happening with your antimony and lead –– I'm only on my third chemistry class –– but it sounds like it, given the low temperature and the brittleness of the result. You can watch videos on YouTube of mercury or gallium doing this to aluminum, even at room temperature. The process is called amalgamation.

    At a high enough temperature, the lead and antimony would melt and become a "homogenous solid solution," which is über-nerd technical term for any alloy. Concrete might be a good analogy for what you're getting at the lower temp. Instead of being homogeneously distributed throughout the lead, the antimony is in irregular clumps, like gravel in concrete. When you bend or drop your lead-antimony, instead of the lead atoms sliding past each other and distributing the force by deforming (what malleability means), that force smacks into the clumps of antimony, which is more than 10x harder and 4x less malleable than lead. That smack acts like a focal point, and the malleable lead rebounds away from the harder antimony, creating shearing that propagates between antimony clumps until the force is used up, either by this shearing or by pieces completely separating.

    I would do a test with a small piece of your lead-antimony by re-melting, adding 50-100% more lead, then once it's cooled try to hammer it flat to see if it's malleable or still brittle.

    Tin lowers the melting point of bismuth, but I don't know if it would with antimony and lead. You could repeat the above test and see.

    If you don't find someone more knowledgeable, and you're feeling adventurous, the red-hot center of a wood fire in a fireplace can reach more than 1,800 degrees, and a kiln for pottery can go even higher. All you'd need is a crucible or oven-safe ceramic bowl. Be sure to put the bowl of metal in before you light the fire or kiln, because putting room temp ceramic in a hot fire can crack it.

    I wish I had more-useful info for you, but I hope some of this helps.
     
  13. DLS

    DLS
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    Well I got into the garage a bit this weekend. I took the 50/50 lead/antimony ingots and re-alloyed them down to just 25% antimony. They cast well and are not brittle, so will store well too. So they are ready for future mixing depending on what bullet I want to cast.

    I've been using pure lead from a supply of old roof flashing material. This weekend I also melted all of this pure lead down and cast into ingots to ease future alloying. I was cutting strips with tin snips to feed into my casting pot ... a very labor intensive method. But I was focusing on creating the Pb/Sb alloy, not efficient casting, and I had time to kill as the melt heated. This supply of lead seemed to be very clean, but I found it to have a great deal of junk floating to the top once melted. It's clean now but I'm wondering if some of the inclusions messed with my alloy attempts earlier?
    Time will tell, sometime this week I'll go at it again (alloying my pure antimony with my pure lead) but shoot directly for the 25% antimony ratio. I'll pre melt the lead and then float the antimony on top and let it sit (no additional torching from above) to see if it will actually go into the melt as some of the internet pundits state. That way I'm not dealing with the antimony trioxide smoke my earlier method produced.

    I have read that tin helps the antimony to go into solution ... so I'm still wondering if I should put some tin into the mix from the get go. Any thoughts would be appreciated on this.
     
  14. Crohnos01

    Crohnos01
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    I am just getting into bullet casting myself and I am following this thread with great interest. I used to work with pouring lead joints when I was in the plumbing trade... Many, many moons ago.
    I am looking to cast pure lead bullets for paper patch rounds and have a fair supply of pure lead to work from. After reading the above, how does one remove antimony from an alloy once mixed? Or is that possible?
     
  15. DLS

    DLS
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    Heating up the mix and letting the surface contact the air will create tin and antimony oxides. They look like silver oatmeal on the top of the melt. Skimming this off rather than fluxing it back into the melt will remove these alloying elements.

    If you have a lot of alloyed lead, it may be better to trade that for pure lead. It's a shame to lose those expensive ingredients.

    Paper patching looks interesting ... I have a couple of old NRA article reprint books that detail the process. I've never had a suitable rifle to try this with.
     
  16. Crohnos01

    Crohnos01
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    Thanks DLS;

    If I get this worked out and you're interested, we should swap information; maybe hang out for a lead melt party? I am in BG as well, so should be easy to make connections depending on schedules.

    Regarding the paper patch; from my reading it seems pretty interesting. I have a 45-70 Sharps I am going to try it on, but it seems like folks are using them on more modern calibers as well. I don't know to what level of success, but if I get the 45-70 worked out, I may try something with a couple of my 30 caliber weapons just for fun.
     
  17. DLS

    DLS
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    A 150gr hand cast, paper patched bullet for the Garand! Now that would be fun to show up to a match with rounds like that. If you could shoot good scores think how it would mess with the other guys minds! LOL

    The reason I'm messing with harder alloys is that I want to start casting for rifles, especially my mil-surps. I want to reduce the barrel wear but still have reasonably accurate enough rounds to shoot a couple hundred yards without undue handicap.


    I've cast a ton of pistol rounds over the years ... straight wheel weights for most of it since they were mostly match / plinking loads.
     
  18. DLS

    DLS
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    Crohnos ... what do you have for a melting set up? I have a Lee 10# bottom pour that for years I did everything in. I now use a camp stove and 8inch cast iron fry pan for allowing and cleaning metal. The stove is slow to melt, so I use a weed burner to accelerate the melt when I'm in a hurry. I'd love to have a turkey fryer type of burner. If I did I would cut the bottom off an old propane tank to make a decent sized crucible and then could really clean and alloy large batches at once.
     
  19. P7id10T

    P7id10T
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    Each different metal provides different effects in the alloy process. Tin (Sn) may assist in the distribution of the Antimony (Sb) in the solution. Tin's most important effect is to improve the flow, giving you a much better cast.
    Small amounts of copper (<2%) can increase the hardness while not affecting the flow.
    Zinc would have the opposite effect, ruining the flow characteristics of the melt and if enough is present, cause the elements to separate out.

    Got any extra Antimony you want to sell ?
     
  20. P7id10T

    P7id10T
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    Ceramic crucibles can be found inexpensively on Amazon. If you have access to old high pressure gas bottles (argon, CO2, etc), cutting off the bottom can make an awesome crucible.
     

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