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Thread: Is there a formula for lowering the BHN of your lead

  1. #1
    Boolit Mold
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    Question Is there a formula for lowering the BHN of your lead

    Not the normal question, as everyone wants to harden their lead , I understand. I have a great deal of age hardened alloyed lead that is testing at 16-18 BHN and harder. I want to do some testing on a certain caliber based on bullet weight and max pressures. The formulas that I have used suggest I would be needing BHN 12, as being hard enough for the max pressure and soft enough to seal the bore properly and for the speed it will be travelling. I know a ton of people will say , it doesn't matter, that they don't care, as every bullet will go down the bore. According to a good deal of people making video's out there, certain BHNs should be used for certain FPS and there are optimal pressures for bore sealing and max pressures that a BHN can take before issues arise, and I would like to experiment with that in mind. Does anyone have a formula or a tested practice that I can dilute my 10#s of 16-18 and bring it down to 12 ? Again, I know it's not a common question, but it is one I have. Food for thought for some while a total waste to others, again I understand.

  2. #2
    Boolit Master
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    Do a search for the alloy calculator here on the forum.
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  3. #3
    Boolit Master
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    Yes you can blend pure (or near pure) in with what you have to get softer.

    However, please note that hard lead is "hard to come by" now days and most scrap lead available in large quantities is on the soft side.

    Unless you have hard lead by the tons, you do not have "a lot" of hard lead.

    Trading with someone local is one of the best method to get a different BHN.

    Also, if you can find some "range lead" it will probably be closer to 10 BHN. Throw in some of you hard and it will be closer to 12 BHN.

    Another thing you should probably try is to check out local scrap yards to see if any will sell to you. If so, most of what they have will be softer than what you want. However, you may get luck and find some that is not "dead soft".

  4. #4
    Boolit Master

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    TEST a theory using a simple ratio on a small sample, which might work for you.

    Melt a small batch, (WEIGHTa) of 0.25 pounds of alloy (BHN=18). Thus WEIGHTa * 18BHN = 4.5#BHN

    Melt into that, (WEIGHTb) 0.25 pound of soft lead (BHN=6). Thus WEIGHTb * 6BHN = 1.5#BHN

    The resulting alloy, in this case (WEIGHTa + WEIGHTb) of 0.5 pounds should have a BHN=12.

    FORMULA

    = [(WEIGHTa * 18BHN) + (WEIGHTb * 6BHN)] / [(WEIGHTa + WEIGHTb)]

    = (4.5#BHN + 1.5#BHN) / 0.5#

    =12BHN

    The ratio works for other weights and other BHN's. Just change the numbers to suit.

    NOTE
    It is not known if unspecified chemistry (i.e. arsnic, antomony, tin, etc.), will affect the outcome...
    If it was easy, anybody could do it.

  5. #5
    Boolit Buddy 414gates's Avatar
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    The diffference between 12 and 18 BHN may not be important.

    Neither is hard or soft.

    Cast a few bullets and test. My guess is you will not see any difference between the two for your application, even if the formula asks for BHN 12.

    Sizing correctly in relation to the bore diameter takes care of bore sealing.

  6. #6
    Boolit Master

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    Do you know the history on the lead? Rate of cooling can affect hardness. Have you used some of this lead to cast bullets recently?

    If not, I would cast a few bullets and check hardness on newly cast, 72 hours later, and a couple weeks later. Possibility is that maybe it isn't as hard as you think.

    If you know the history and ingots were in fact air cooled, then proceed.

    But really, usability between 12 and 18 bhn is not really that much. I'd try what I had first. You might find that 12 bhn might be too soft for your purposes and then you'll be looking to re-harden your alloy.

  7. #7
    Boolit Mold
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    Quote Originally Posted by BK7saum View Post
    Do you know the history on the lead? Rate of cooling can affect hardness. Have you used some of this lead to cast bullets recently?

    If not, I would cast a few bullets and check hardness on newly cast, 72 hours later, and a couple weeks later. Possibility is that maybe it isn't as hard as you think.

    If you know the history and ingots were in fact air cooled, then proceed.

    But really, usability between 12 and 18 bhn is not really that much. I'd try what I had first. You might find that 12 bhn might be too soft for your purposes and then you'll be looking to re-harden your alloy.
    Morning. Do I know lead history, a little. Do I understand the cooling and hardening effect, yes. Do I know the history of my pile of lead, no. I have hardened many times but have never run into this testing issue. I have tested the lead many times, two different ways to verify BHN. By all the formulas out there, in theory the 12 BHN should be very efficient. Bullet sized to bore, so it’s not an issues. Like I said, all bullets will go down the bore , but you might gain or lose performance due to the bore not getting sealed properly or you might get gas cutting which will give you possible leading and a loss of fps. I do believe formulas and books were invented and written to deal with all these issues and if it’s not really important, why bother ? And again, some people don’t give a dam just like cleaning brass, some shine it to a mirror and some just wipe it off, to each their own. I on the other hand have over thirty units that I cast and load for and I try to get the best out of them all. I was/ am looking for a percentage of pure lead to mix to get me to where I want to be for different firearms. Thanks for your response.

  8. #8
    Boolit Mold
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    Bullet is properly sized to bore, so that is not an issue. Differences in BHN does come in effect due to the max pressures of loads and that’s what I am trying to achieve. The 18 BHN I have is a waste in lower power loads. And like I said some wouldn’t care as everything will go down the bore. In all fairness , why cast , why harden lead if you feel there is no big difference? You might has well just go buy hard cast 21 BHN and shoot away. I try very hard to get the max out my firearms and am loosing for suggestions to help me get to where I want to be. Thanks for your reply.

  9. #9
    Boolit Mold
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    Quote Originally Posted by Land Owner View Post
    TEST a theory using a simple ratio on a small sample, which might work for you.

    Melt a small batch, (WEIGHTa) of 0.25 pounds of alloy (BHN=18). Thus WEIGHTa * 18BHN = 4.5#BHN

    Melt into that, (WEIGHTb) 0.25 pound of soft lead (BHN=6). Thus WEIGHTb * 6BHN = 1.5#BHN

    The resulting alloy, in this case (WEIGHTa + WEIGHTb) of 0.5 pounds should have a BHN=12.

    FORMULA

    = [(WEIGHTa * 18BHN) + (WEIGHTb * 6BHN)] / [(WEIGHTa + WEIGHTb)]

    = (4.5#BHN + 1.5#BHN) / 0.5#

    =12BHN

    The ratio works for other weights and other BHN's. Just change the numbers to suit.

    NOTE
    It is not known if unspecified chemistry (i.e. arsnic, antomony, tin, etc.), will affect the outcome...

    Big thanks, well worth the try !

  10. #10
    Boolit Mold
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    Quote Originally Posted by P Flados View Post
    Yes you can blend pure (or near pure) in with what you have to get softer.

    However, please note that hard lead is "hard to come by" now days and most scrap lead available in large quantities is on the soft side.

    Unless you have hard lead by the tons, you do not have "a lot" of hard lead.

    Trading with someone local is one of the best method to get a different BHN.

    Also, if you can find some "range lead" it will probably be closer to 10 BHN. Throw in some of you hard and it will be closer to 12 BHN.

    Another thing you should probably try is to check out local scrap yards to see if any will sell to you. If so, most of what they have will be softer than what you want. However, you may get luck and find some that is not "dead soft".

    For me, I have tons of lead, for you maybe not. I do understand I can soften, but I can’t figure out percentages. That’s why I asked so that I don’t waste a great deal of time. Thanks for your reply.

  11. #11
    Boolit Master

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    The reason for my questions is that I havevrange lead ingots that air cool to 10-10.5 bhn, but have a higher bhn when I cool them rapidly on a wet towel locayed beneath my ingot molds.

    If you don't know the history on your lead amd haven't remelted and aircooled a sample, can you really be sure of the "air-cooled" ingot bhn? It is probavly not an issue, but i would hate to soften an alloy of unknown origin to find that it turned out a lower bhn than I intended.

  12. #12
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    Quote Originally Posted by poppy42 View Post
    Do a search for the alloy calculator here on the forum.
    I have used calcs to harden many many times, but do not know if I can use a calc to soften a mix, because the calcs are/were designed for hardening as far as I have seen, but I may be missing something as this softening is new to me.
    Last edited by HIGHRPM; 11-18-2022 at 12:54 PM.

  13. #13
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    in the opening, you said you had 10#s of 16-18 bhn lead you needed to soften. I think we were all under the assumption you had a limited supply. Later you say you have tons of lead.

    Alloy away and if it isn't right add a little more of this or that until it is what you want. I and maybe others did not want you to screw up a limited supply. Since you have tons, play around with the alloys until you get it right.

  14. #14
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    Quote Originally Posted by BK7saum View Post
    The reason for my questions is that I havevrange lead ingots that air cool to 10-10.5 bhn, but have a higher bhn when I cool them rapidly on a wet towel locayed beneath my ingot molds.

    If you don't know the history on your lead amd haven't remelted and aircooled a sample, can you really be sure of the "air-cooled" ingot bhn? It is probavly not an issue, but i would hate to soften an alloy of unknown origin to find that it turned out a lower bhn than I intended.
    I do understand the different cooling methods and the age hardening and no, I have not done anything with this lead since testing hardness. And if I could figure out a percentage per weight of ingot to add pure lead to get me close that’s all I am looking for. But I do not want to blindly wing it and waste time, that’s why I asked.

  15. #15
    Boolit Mold
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    Quote Originally Posted by BK7saum View Post
    in the opening, you said you had 10#s of 16-18 bhn lead you needed to soften. I think we were all under the assumption you had a limited supply. Later you say you have tons of lead.

    Alloy away and if it isn't right add a little more of this or that until it is what you want. I and maybe others did not want you to screw up a limited supply. Since you have tons, play around with the alloys until you get it right.
    I listed the 10# as an example of what I need to blend so if someone knew they could give me a percentage per the 10#s. I do have a couple thousand pounds of lead . And again don’t want to play around and waste time, not my preferred way of doing things. Just asking, as we all know different things and the best way to learn things is to ask and then do. Imho

  16. #16
    Boolit Master

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    Quote Originally Posted by HIGHRPM View Post
    I have used calcs to harden many many times, but do not know if I can use a calc to soften a mix, because the calcs are/were designed for hardening as far as I have seen, but I may be missing something as this softening is new to me.
    Not sure that I understand that statement. Altering the ratios will get you harder or softer. Perhaps this calculator will work for you, simply choose the alloy best reflecting your current hard lead and then keep adding XX of soft and hit the calculate button. You can also alter the ratio of components from the programs preset ratios. This is an older calculator and may not be the best available but it works for this simple old man.

    http://www.weatherby.dk/bhn.htm

    note added: I just pulled the calculator up and selected Clip-on weights and then bumped the antimony up to 9.5-10% and tin to 3% to get your starting 18+ BHN then I selected the stick-on weights and added 1.75 pounds and got a 12.31 bhn. Just play with your input ratios a bit. Trial and error, it is what it is.
    Last edited by oley55; 11-18-2022 at 03:39 PM.
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  17. #17
    Boolit Buddy wilecoyote's Avatar
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    Quote Originally Posted by oley55 View Post
    Not sure that I understand that statement. Altering the ratios will get you harder or softer. Perhaps this calculator will work for you, simply choose the alloy best reflecting your current hard lead and then keep adding XX of soft and hit the calculate button. You can also alter the ratio of components from the programs preset ratios. This is an older calculator and may not be the best available but it works for this simple old man.

    http://www.weatherby.dk/bhn.htm

    note added: I just pulled the calculator up and selected Clip-on weights and then bumped the antimony up to 9.5-10% and tin to 3% to get your starting 18+ BHN then I selected the stick-on weights and added 1.75 pounds and got a 12.31 bhn. Just play with your input ratios a bit. Trial and error, it is what it is.
    Oley55, thanks about the calculator link !
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  18. #18
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    Quote Originally Posted by wilecoyote View Post
    Oley55, thanks about the calculator link !
    you are more than welcome Sir. I don't honestly know how accurate the calculations are since I only rely on drafting pencils. I have used it for making guesstimates of how much of what alloy I would need to purchase to harden my many hundred pounds of soft roofing stacks lead. At any rate I should think it will be useful to the OP if he plays with it a little.
    “Some people spend an entire lifetime wondering if they made a difference in the world. But, the Marines don't have that problem.” Ronald Reagan


  19. #19
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    ...for the simple old man here not well versed in math., never been, that's a BIG help, or at least my next excuse to try & play !
    ...next thing you know they'll want your pistol and your tobacco...

  20. #20
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    I tried weighted averages to calculate alloy hardness, but I couldn't get it to correlate with actual hardness. It especially gets confusing when the alloy isn't just lead:tin. Add antimony and a little arsenic, and Katy bar the door...
    You COULD plot alloy hardness as a function of tin content. 40:1 alloy would be softest, followed by 30:1, then 20:1, then 10:1. This will give rise to a curve, the equation of which can be obtained by least squares, and then the hardness (Y) can be estimated by tin content (X). Anyway, a 10:1 alloy (9.1% tin) will not have a hardness 4 times as great as a 40:1 alloy (2.44% tin), and a 20:1 alloy (4.76% tin) will not have a hardness twice that of 40:1, so I doubt that weighted averages are the answer, here.
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