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Thread: Whats the brownish stuff?

  1. #1
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    Question Whats the brownish stuff?

    I was cleaning my upper from a top name brand company and noticed some brownish rust like stains on the inside of my chamber just past the lugs. Tried a chamber brush and chamber mop and it won't come off. What gives? The upper is about 7 months old with around 150 rounds down the pipe and it was bought new.

  2. #2
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    assembly grease maybe ?

  3. #3
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    Get some solvent, take a section out of a USGI cleaning rod, attach USGI chamber brush, chuck in cordless drill on low speed, dip brush in solvent, insert brush into chamber, and go slow for about 10 seconds. Wash out with brake cleaner. Wipe down with oily rag, and be done with it.




    As said its likely assembly/preservative grease that dried up, and then was probably baked on by shooting. Always give a new gun/upper a good cleaning before shooting to get all that junk out of there.

  4. #4
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    That's the thing that is getting me. I cleaned the piss out of it like any new gun I buy and I am not sure why I just now noticed it. I tried the cleaning method you suggested and it's still there. Oh well. I am sure it's not rust as it is still new.

  5. #5
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    What would be the 'top name brand company'?

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    I have a 14.5" LMT that has had discoloration in the chamber/lug area that has seen between 5000 and 6000 rounds with no problems. The carbine is almost never white glove clean so I haven't noticed the discoloration latley. I just shot the thing and didn't put too much thougt into it as it was surface discoloration and there was no visible pitting/rust etc..

    It came up on 10-8 forums with another LMT a year or two ago. IIRC the op in that thread had no problems other than the discoloration YMMV.

    I would contat the maufacturer to see if this is normal or a possible QC problem.
    Robert

  7. #7
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    This is what the company recently stated.
    (It is chromic acid (brown residue) which is used during the phosphate procedure at a very low dosage) Sound right?

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    i would have guessed assembly grease also.

    But ya i don't see why it can be a stain from chromic acid.
    that would also be the answer why doing solvent, wire bore brush, low speed drill
    had zero effect.
    Rust would have came off or at least mostly came off, I'd say don't worry
    it's just a stain inside the chamber.



    However i did hear there was some bad Brown chromic acid going around.
    Stay away from the bad brown chromic acid.

  9. #9
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    What kind of affect can it have down the road?

  10. #10
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    Quote Originally Posted by Jason Markert View Post
    This is what the company recently stated.
    (It is chromic acid (brown residue) which is used during the phosphate procedure at a very low dosage) Sound right?
    It could very well be true, it happens to a lot of the parts my company does. Doesn't affect the coating, its just not pretty.

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