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Thread: Alloys & Barrel Conditions

  1. #1
    Boolit Master

    Join Date
    Apr 2010
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    Oklahoma
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    Alloys & Barrel Conditions

    I’m comparing 3 alloys, all of which (by Bumpo’s Calculator) are at an estimated hardness of 13.0.

    Alloy 1: Antimonial Lead at 5% Sb, 95% Pb
    Alloy 2: 1.56% Sn, 4.34% Sb, 0.23% As, 93.9% Pb
    Alloy 3: 3.12% Sn, 3.81% Sb, 0.21% As, 92.8% Pb

    My question is would a barrel react differently in terms of leading, antimonial wash, etc between these 3 alloys? All are at a hardness of 13.0.

    Assuming the load is adequate to the strengths of the alloys; boolits sized correctly etc., could the alloy(s) composition result in differing barrel condition(s) between the different alloys? Or should they all behave the same due to all being of the same hardness?

    Another question, what if one was to water drop 25:1, 20:1, 16:1 etc to achieve a hardness of 13.0, (assuming these would harden without antimony / arsenic) would all of these alloys behave the same within the barrel?

    Just curious…
    Last edited by PbHurler; 11-28-2018 at 09:37 AM. Reason: Water drop addition
    Bob

  2. #2
    Boolit Master Harter66's Avatar
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    No is the simple answer .

    I'm guessing that #1 will have a high reject rate and be fragile . #3 is going to be the best bet for all around ingot to target . If #2 casts well it will likely be the highest velocity capable bullet but also 2nd most likely to break up on impact .
    The lead alloys won't quench harden at all .
    All of this is subjective of course because there is no information about cartridge , use , or target speeds .

    Thoughts to think .
    Elmer Kieth developed what would become the 44 magnum with 1:16 tin/lead and gas checks .
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    I was young and stupid then I'm older now. Me 1992 .

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  3. #3
    Boolit Bub
    Join Date
    Dec 2009
    Location
    Ball Ground, GA
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    I'm not sure I can answer your question completely but here goes. The 3.1sn/3.8sb is not going to be 13 brinell acording to my lee tester. My Gas check rifle alloy is 2.5sn and 3.5sb and it measures closer to 14.5/15.0 so I suspect your alloy to be higher than that, maybe 16/17 birnell.
    I am not stating that as fact, just that is what my tester reads. Out of the three alloys you listed, that would be a good alloy for higher velocity cast boolits and maybe a good hunting alloy for flat nosed boolits.
    Alloy #2 is also a good all around alloy except I think the Antimony content is a little high depending on what you are trying to accomplish.
    The 5% antimony alloy I have never cast with so no personal experience but 13 brinell sounds a little high for that but I'm not sure, maybe "runfiverun" will respond, I think I've read he has some knowledge in that area.
    As to your question of equal hardness resulting in equal performance the answer is "no". Too many variables from gun to gun, powder, primers and the list goes on and on. The alloy has to match not only the internal, "case to muzzle" but also the external "target" requirements. Brinell hardness should not be the first goal in alloy development. My first goal is the terminal performance, hunting or target. Second is the accuracy requirement. Third is the cartridge, 38 special or 30-06 or 45-70. All three of these could use the same alloy without regard to terminal ballistics. My soft alloy is great in 38 special but shoots like a shotgun pattern in the 06. But my 06 alloy is also very accurate in the 38 special if I get above 850 fps. Match the alloy to your purpose. 20:1 shoots great in the 45-70 and the 38 special but not so good in the 30-06. Soft alloys like 20:1 in handguns and big bore rifles is not hard to get accurate loads. In bottleneck rifle cases, my best alloy's are 1.5 to 2% tin and 3.0 to 3.7 antimony range for paper punching. For hunting in bottlenecks a balanced tin and antimony to match your terminal performance needs ie... velocity at your expected impact range, a little tricky, just requires a little more load development and testing.
    Tony

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check