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  1. #1
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    Question How to Tell if Ammo is Corrosive

    I have heard that the old military surplus corrosive ammo has primers that are round, while the non-corrosive stuff has flat primers like you would find on American non-corrosive ammo. Has anyone heard of this? I bought a spam can of 5.45 and it's supposedly corrosive but the primers are as flat as any other centerfire cartridge I have.

    ETA: I compared the 5.45 to some surplus 7.62x39 and the 7.62 does have round primers.

  2. #2
    TGT Supporter Texasjack's Avatar
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    For American ammo, the date of manufacture is the means of determination and can be looked up. For foreign stuff - well, you kinda take your chances.

    The material used in the primers changed from (corrosive) mercuric fulminate to (noncorrosive) lead azide. The design (and therefore shape) of the primers did not change.

    You can use corrosive primed ammo, but you have to be pretty religious about cleaning after firing.

  3. #3
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    I heards of a way to figure out if they are corrosive. Pull a bullet and powder (with any kinetic bullet puller). Load the round into a gun, and point it at a piece of steel (in a safe direction, of course. I'm pretty sure it is steel, but I could be wrong). Clean the gun as if it is corrosive ammo. If it is corrosive, it will rust the steel pretty quickly.
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  4. #4
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    Quote Originally Posted by Texasjack
    For American ammo, the date of manufacture is the means of determination and can be looked up.
    Any idea what the date to look for may be?
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  5. #5
    TGT Supporter Texasjack's Avatar
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    CW, here's an article on how to tell if it's corrosive. For US stuff, it's mostly pre-1954.

    Corrosive Primer Redux (.pdf)

  6. #6
    TGT Supporter Texasjack's Avatar
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    Another interesting document:

    MSDS for Winchester Primers (.pdf)

  7. #7
    TGT Supporter Texasjack's Avatar
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    It's OK to FIRE corrosive primed ammo. What happens is that the mercury compounds for corrosive salts that are hygroscopic (attract water). If you leave the barrel dirty, it will corrode quickly - much like it would if you exposed the barrel to salt water. Mercury itself doesn't damage steel. Gunsmiths used to use mercury to dissolve bullets stuck in muzzleloaders. It's the corrosive salts that cause the problem. If you clean the barrel after every use, you'll be OK.

    Mercury does attack and quickly weaken gold, silver, lead, aluminum, copper, or brass. So it's not good to have it around ammo or guns with nice inlays.

  8. #8
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    Thanks for the resources, Texasjack.
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  9. #9
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    Quote Originally Posted by Texasjack View Post
    It's OK to FIRE corrosive primed ammo. What happens is that the mercury compounds for corrosive salts that are hygroscopic (attract water). If you leave the barrel dirty, it will corrode quickly - much like it would if you exposed the barrel to salt water. Mercury itself doesn't damage steel. Gunsmiths used to use mercury to dissolve bullets stuck in muzzleloaders. It's the corrosive salts that cause the problem. If you clean the barrel after every use, you'll be OK.

    Mercury does attack and quickly weaken gold, silver, lead, aluminum, copper, or brass. So it's not good to have it around ammo or guns with nice inlays.
    I remember reading something about amonia baths for shooting corrosive ammo. Think you were suspose to soak your barrels in it or something.

  10. #10
    TGT Supporter Texasjack's Avatar
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    I've seen some posts about using ammonia cleaners (like window cleaner) to scrub your gun. That's pretty much unnecessary. (Although the ammonia will help get rid of copper deposits.) The idea is that the mercury salts are soluble in water and the ammonia is supposed to reduce the acidity. If you clean the gun like you should, you'll get the salts out. After all, up until the late 1950's, ALL ammunition used corrosive primers! People who took care of their guns didn't have problems.

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