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Thread: Gas Check Tarnish

  1. #1
    Boolit Master

    Walks's Avatar
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    Jun 2016

    Gas Check Tarnish

    Recently I had to dig out an old box of .357Mag Gas Checked Bullets.

    Some Lyman #358156, these were cast from 35 - 40yrs ago. And Checked with a combination of old Lyman brass slip on and Hornady copper crimp on.
    The brass gas checks were as bright, shiny and clean as the day they came out of the box. The copper checks were heavily tarnished and discolored.

    Can't figure out why the copper were tarnished and the brass were not.

    They were stored in a cardboard box, just dumped in. Bottom, back shelf. Untouched for 30yrs.
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  2. #2
    Boolit Master

    Winger Ed.'s Avatar
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    May 2007
    East Texas
    Different Brass and Copper alloys tarnish at different rates.

    I've got a bunch of crimp ons from the 80's, and they're a little tarnished.
    I ran some of them in the polisher so they'd look pretty, and they still work.
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  3. #3
    Boolit Master

    skeettx's Avatar
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    Jul 2009
    Amarillo, Texas
    Some cardboards outgas as they age
    This is most likely what caused the changes
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  4. #4
    Boolit Master redhawk0's Avatar
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    Apr 2016
    North East, USA
    Brass is a combination of Copper and Zinc....Zinc is an "anti-corrosive" additive as well as a hardner. Its in small quantities, but its enough to keep the tarnish rate much lower that pure copper.


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  5. #5
    Boolit Master

    gwpercle's Avatar
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    Sep 2011
    Baton Rouge, Louisiana
    My old copper checks have all turned a dark brown's just the nature of a metal high in copper .
    Look at old copper roofing or roof flashing...the good stuff will be a dark brown .

    My checks were stored in the small round tin can they came in (can't remember if Lyman or Hornady)
    and they still turned brown ... it doesn't hurt them , go ahead and use them .
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  6. #6
    Boolit Master
    Join Date
    Jan 2006
    So. Cal.
    Copper roofing turns GREEN. Especially if it is acid washed.

  7. #7
    Boolit Buddy
    Join Date
    Mar 2011
    Northern Illinois
    It's possible someone in the past annealed the copper gas checks. I don't as a rule anneal gas checks but I had some troublesome .22 checks that I annealed and they turned very dark.

  8. #8
    Boolit Master
    Tom W.'s Avatar
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    Mar 2005
    Phenix City, Alabama
    If you use them, when you shoot them you'll probably never see them again. And I'd bet they would work just as well as a brand new one.
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  9. #9
    I'm A Honcho!

    DukeInFlorida's Avatar
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    Oct 2009
    East and South of you
    Well, it might be more chemically correct to suggest that zinc is a "sacrificial metal" . It gives up it's ions more readily than other elements. It's the reason zinc "anodes" are used in marine environments, especially on aluminum engine parts exposed to water.

    So, copper will indeed oxidize faster than brass. Cartridge brass, btw, is also called 70-30 cartridge brass. 70% copper and 30% zinc.

    Quote Originally Posted by redhawk0 View Post
    Brass is a combination of Copper and Zinc....Zinc is an "anti-corrosive" additive as well as a hardner. Its in small quantities, but its enough to keep the tarnish rate much lower that pure copper.


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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