Ammo corrosion

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  • Mr. B

    Active Member
    Jul 9, 2019
    132
    MD
    Howdy all,

    I've moved from .40 to 9mm and have a stockpile of .40 ammo. A young friend mentioned he needed some more 40, so I told him I'd let him have as much of my excess as he wanted - cheap.

    This PMC .40 165gr has been in my basement for close to 20 years, and upon inspection the cases show some corrosion (see pic).

    I don't know what, if any, problem this level of case corrosion pose, and I don't want to sell or give this stuff to a friend if there might be issues.

    I'd like to hear from the experience and wisdom of MDS.

    Thanks in advance
     

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    Threeband

    The M1 Does My Talking
    MDS Supporter
    Dec 30, 2006
    25,233
    Carroll County
    That doesn't look like corrosion at all. It looks like it's just lost its shine.

    I've shot lots of surplus that had real corrosion. The CMP used to sell surplus .30-06 that had stripes of brown or whitish corrosion running lengthwise down some cases.

    I've got a bunch of surplus 6.5 Swede that would send you screaming on down the road, yet it shoots fine.
     

    DutchV

    Ultimate Member
    Jul 8, 2012
    4,703
    That's just a little tarnish; no big deal. Corrosion would be green.
     

    willtill

    The Dude Abides
    MDS Supporter
    May 15, 2007
    24,328
    Wait until you fire 8x56mmR WW2 era ammo. Looks fine but can infrequently rupture it's case. Like a black cat firecracker going off in your face.

    Wear my safety glasses and a ballcap when firing my Mannlicher M95/30 rifles. They're a hoot :)

    Truth be told, you can't judge the integrity of old ammo from the outside.
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,733
    Socialist State of Maryland
    You get that kind of tarnish for several reasons. If you store your ammo in plastic containers that gas over time, or near a water conditioner, or your humidity is a little high. It doesn't hurt anything and is perfectly safe.
     

    Jed195

    Ultimate Member
    Oct 19, 2011
    3,901
    MD.
    Fired some old(20yrs) 5.56 out of my AR up at elk neck. Fired fine-but left a smoke trail like a line from the muzzle to the target-kind of like a smoke tracer.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    Actual corrosion will show up a colored powdering looking deposits.

    Typically green corrosion, which can be buffed or tumbled off. You used to see a lot of this when people (cops) carried spare rounds in loops on their leather belt.

    If you see pink corrosion, DO NOT FIRE THE AMMO. The pink corrosion eats into the case, and can cause case failures. Much of the pink corrosion is reported in ammo that is in ammo boxes that have excess acid Unfortunately, so of the battle packs of 7.62 is like this.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Fired some old(20yrs) 5.56 out of my AR up at elk neck. Fired fine-but left a smoke trail like a line from the muzzle to the target-kind of like a smoke tracer.

    Really humid day? That’s what a bulletin trace is from. It’s vapor condensing out of the atmosphere from the low pressure wake of the bullet. Normally hard to see unless it is very humid.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    If you have a brass tumbler that uses corncob media or similar, just run it through that, and it'll get shiny again. There's no issue with tumbling live rounds, and it's actually sometimes helpful on older milsurp to get them a little cleaner to do a true corrosion assessment.

    But, really, I'd just shoot it.
     

    Jed195

    Ultimate Member
    Oct 19, 2011
    3,901
    MD.
    Really humid day? That’s what a bulletin trace is from. It’s vapor condensing out of the atmosphere from the low pressure wake of the bullet. Normally hard to see unless it is very humid.

    In designated marksman training we got used to watching the vapor trails of our tricked out M14s and M40A2s rounds. Got good enough to call the shot based on the trails.
     

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