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Thread: Lead Hardness Question

  1. #1
    Bob Lintner is offline
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    Question Lead Hardness Question

    Got some lead that checks out at 6-7 brinell hardness. Is this ok for muzzleloader rifles and c&b revolvers? Thanks. Bob

  2. #2
    Lou Lou Lou is offline
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    Somebody will correct me if I am wrong, but I believe that pure lead has a BHN of 5. BHN of 6-7 "should" be ok. If your minie's have thick skirts, it might be an issue.
    Melt it, cast it, load it and shoot it. Empirical testing.
    Lou Lou Lou Ruggiero
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    5 or less is considered pure lead. Up to 5.5 or 6 I usually try to mix with some softer stuff, but higher than that I use for my smoothbore and Smith carbine.
    Gary Van Kauwenbergh
    Co G, 114th ILL Vol Inf
    # 10143

    "Alle Kunst ist umsonst Wenn ein Engel in das Zündloch prunst."
    (In vain the skill and arts of man, When an angel pisses the priming pan.)
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    Here is what the NRA's publication of Col. Harrison's "Cast Bullets" states with regard to bullet BHN hardness of various tin to lead ratios:

    Lead only 5 (else where he states pure lead is 4.5 to 5 on the BHN scale.
    1:40 8.5
    1:30 9
    1:20 10
    1:10 11.5

    It would be interesting to do a polynomial curve fit to those numbers to get an equation so that one could calculate the hardness of 1:160 (1 oz tin to 10 lbs of lead) for example. I'll give it a shot and let you know what I come up with.


    Pat

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    Okay, here's the equation I get when with the limited number of data points I have is used to fit a 2nd degree polynomial curve to them:

    BHN= -785.9*ratio**2+141.93*ratio+5.1237 where "ratio" is the weight of the tin divided by the weight of the lead in the alloy of interest. The R**2 value of the curve fit was .99+ which means its a pretty good fit to the data points. An R**2 equal to 1.0 means an exact fit.

    I'm using the * to mean multiply by and the **2 to mean multiply the ratio by itself twice (the number squared (in mathematical terms)).

    Following the order-of-computation rules of math I would suggest that you compute the squares first, then do the simple multiplies second, and then any additions or subtractions third when using this equation. Better yet let a spreadsheet do the math for you with the ratio set up to be a replaceable variable value.

    Anyway, I tried a 1 oz tin to 80 oz (5 lbs) lead alloy ratio which equals a ratio of .0125.

    Plugging that ratio into the equation the calculated BHN is 6.775.

    Going for 1 oz tin to 160 oz lead (10 lbs), ratio = .00625, we get an estimated BHN of 5.980.

    Going for 1 oz tin 10 320 oz lead (20 lbs), ratio = .003125, we get an estimated BHN of 5.559

    The shape of the polynomial curve in the region of interest is almost linear so you can use linear interpolation between these calculated numbers above to get a good approximation of the BHN values for other tin to lead weight ratios should you so desire. And, remember these results are simply reasonable approximations of what the true value might be. They'll be close, but not exact.


    Pat

  6. #6
    Bob Lintner is offline
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    Thanks for the great info guys! Sure do appreciate it! Bob

  7. #7
    jonk is offline
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    The softer the better for minies of course; but if you can dent the skirt with a light squeeze it should be soft enough.

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    I understand the BHN scale & agree w/Jonk, WRT lead: softer = better, esp WRT to Minie's.


    Along those lines of Lead Hardness, I'm curious if anyone uses other alternative testing methods?


    In addition to the "squeeze" test, my favorite, is the "ear" test. This preferred technique was good enough for my dad & granddad, and serves me well enough in quickly (and cost effectively) evaluating my lead's BHN scale...

    Taking a cast ingot, I drop it onto my garage's cement floor. If it "rings" or "clinks", it's considered hard lead (carbine/smoothbore use), a "thud" indicates soft lead (musket/revolver use).

    There's also the "fingernail" method, if an ingot can be cut with a fingernail, it's to be considered "soft" lead.
    Semper Fi,
    Rob Freeman
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    I use the "pure lead" test. If the ingot is stamped "PURE LEAD", it's pure lead.

    Steve

  10. #10
    ian45662 is offline
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    When you are casting you allow the puddle on the sprue plate to harden and then you open the sprue plate and drop the bullet. Another sure fire way to tell if your lead is soft is when you open the sprue and it looks like you have ripped lead from the base or the nose of the bullet. The lead is not pure. If after the mold heats up and when you open the sprue it looks like a smear on the base or nose of the bullet you are good. I know its not a good test to figure out what is pure before you cast but it can be used as verification or if what you think is pure is ripping lead from the bullet then its not pure and an adjustment must be made before you cast up a seasons worth of hard minies

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