Odd corrosion ring on BP cartridge

Discussion in 'The Ammo & Reloading Forum' started by Big Mak, Aug 12, 2017.

  1. Big Mak

    Big Mak Well-Known Member Supporting Member

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    Sorry, title should say CORROSION.
    EVER seen anything like this?
    Newer Starline brass, Old Eynsford BP, about 6 months old. All brass cleaned with steel pins in Thumper tumbler and then dried in oven. Sometimes brass sits for months so it is absolutely dry.
    More info: compression is .125 depth. NO air gap ( BP reloaders worst nightmare! )

    Walters vegetable wads and 525 gr boolits with SPG lube used in groove.

    That line is EXACTLY AT THE DEPTH of the 525 gr bullet depth....
     

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    Last edited: Aug 12, 2017
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  2. gdmoody

    gdmoody Moderator Supporting Member

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    I have seen something similar on old ammo.

    BTW, I can fix the title if you want.
     
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  3. Big Mak

    Big Mak Well-Known Member Supporting Member

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    Please do. I've seen it on old ammo too, but not 6 month old with newer brass!
     
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  4. drymag

    drymag Well-Known Member Supporting Member

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    Hard to tell the color, did it get near some other element or picked up some conccentrated lemi or somthing? It's like it picked up the cooties from the die as the marks are on the same spot. Got me?
     
  5. jim brady

    jim brady Well-Known Member

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    Hard to tell from the pictures - but sorta looks like case separation from the picture I looked at. Is the case cracked there? That is the first thing I'd check - to see if that isn't a crack in the case wall.

    Might or might not be the instance, but if you have a really HEAVY crimp, when you fire off the round the bullet is trying to take part of the case forward with it. Just saying...... looks more like gas leaking from the case thru a crack than it does a smudge.
     
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  6. Big Mak

    Big Mak Well-Known Member Supporting Member

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    Drymag, all cases are rinsed in cold water to separate the steel pins from cases so contamination is out of the question.
     
  7. Big Mak

    Big Mak Well-Known Member Supporting Member

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    Jim, the case was not cracked there but rather the corrison was from the inside out to fracture the case. I placed another case side by side to show another line in exactly the same position, without a corrsion break through. Exactly the same distance which is the bullet base bottom.
     
  8. sharps4590

    sharps4590 Well-Known Member

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    What happens if you take a piece of 4/0 steel wool to it? If it cleans up it I'd think it's just BP fouling that etched the case. If not....my next thought was the same as jim's. Other than those two possibilities I don't know. 40 years of shooting BPC's and I've never seen anything quite like that. I had some 45-120 brass that would separate just below bullet seating depth but it was machined and machined cases are junk from the get go. Obviously not the case here.
     
  9. Big Mak

    Big Mak Well-Known Member Supporting Member

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    YOu're correct Sharps, a little steel wool shows the corrosion was from the outside.
    Must have had some greasy fingers (SPG lube) and a granule or two BP stuck there when I put it in the case.
     
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  10. jim brady

    jim brady Well-Known Member

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    Mak - the one case looks like a rounded smudge. The other looks like carbon seeping from a crack. I'm not too sure if cleaning the carbon from the case with the sharp line will tell you anything. A very sharp pin can used to detect a crack on the inside of the case.

    Another thought (if the case isn't separating) is that when you are seating the bullets, you create a slight bulge in the case wall where the bullet stops seating. Could be that even after resizing the case that a small bulge remains. Because black powder residue is so corrosive to brass, a small amount of residue could collect there and stain your cases at that area where there is an imperfection. Just thought I'd throw that idea in.
     
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  11. sharps4590

    sharps4590 Well-Known Member

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    Glad that's all it was. I don't have a wet pin tumbler so my cases NEVER come out that clean. All my BP cases are fouling etched to one degree or another. Some are nearly completely black, such as my 45-90 cases which have been fired a lot. Shiny, clean black, not the corroded black with verdigris present although I have seen that on cases I didn't get as clean as I should have. Just not like yours with such a distinct line and in the same place as what appears to be consistent with yours.

    As Jim said you can test it for a crack with a pin on the outside and a bent wire on the inside. The only difficulties I ever had with BP and cases was the aforementioned machined cases, never with drawn cases.
     
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