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Old March 2, 2013, 06:12 PM   #1
Barnacle Brad
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BN Hardness of Plumbers Lead?

Wondering if anyone knows the BN of plumbers lead? Getting ready to mix 50/50 with it for casting 405g HB bullets for my trapdoor....

Thanks!
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Old March 2, 2013, 06:19 PM   #2
David Bachelder
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Plumbers lead is pure lead. BHN is probably around 5.
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Old March 2, 2013, 06:44 PM   #3
Barnacle Brad
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Thanks David.

The Wolf Trapdoor book has a little section on testing for hardness and lists pure lead as hardness of five, but he also lists plumbers lead separately. The indention for the plumbers lead is pretty close to the pure lead in his table.

I guess in this case close is perfect enough right?

I am new to casting and especially mixing the alloys so I just want to be as informed as I can be.

It will be interesting to repeat the hardness test after I mix the tin and compare to his table.

The alloy I need (20:1) should be around 9.5 - 10 BH. I am mixing 1oz 50/50 solder with 16oz of the plumbers lead.
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Old March 2, 2013, 07:57 PM   #4
mehavey
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If you run actual tests, pure lead comes in well under 5. That said, see below for measurements using actual calculations and actual deformation trials of Brinell material strength (pounds/inĀ²) based on precise alloy mix:


Note that the Lyman #2 test comes in at exactly 14.9 (15 is the industry standard). Note also that all other alloy mixes come in lower than the internet numbers. This is in no small part because the only real testing (and real number) around is on the Lyman 90/5/5 mix. Near all else is the rapid internet spread of supposed-to-be numbers.

Last, note that the OP's 20-1 (will actually be 33-1 as mixed) and be in the BH~ 5.5 range. It might likely shoot just fine (in fact softer lead is rarely a problem in normal velocity ranges, and those ranges can be surprising high)

Last, LAST note is that minor amounts of antimony can cause hardness to vary dramatically -- both because of water quench options (see the super-hard BearTooth BH~24 number at bottom left) and over time (softening -- as with the aged wheel weights coming in under 9 after a couple of years.)




postscript: Actually,1-lb of 50/50 added to 10-lbs of lead will get you (pretty much) 20:1

Last edited by mehavey; March 3, 2013 at 12:27 AM.
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