Build-up scaring on inside of M1 Carbine Slide

Discussion in 'Technical Questions & Information' started by gary.matcek, Jan 1, 2012.

  1. gary.matcek

    gary.matcek Member

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    Happy New Year, All

    I have a National Postal Meter, US .30 caliber M1, with a 1943 barrel. I shoot it often and during cleanings I have notice what appears to be scaring or build-up inside of the slide where the gas cylinder makes contact with slide (see pictures).
    At first I thought it to be powder discharge or carbon that one might expect to leak from the gas port, but the solvents and lubricants I use during cleaning do not reduce or remove.

    Appreciate any advice/ opinion you all my have. Is it common to see buildup at this location ? Is it potentially a hazard or safety concern?

    Thanks,

    Gary

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  2. gary.matcek

    gary.matcek Member

    Joined:
    Jan 17, 2010
    Messages:
    55
    Happy New Year, All

    I have a National Postal Meter, US .30 caliber M1, with a 1943 barrel. I shoot it often and during cleanings I have notice what appears to be scaring or build-up inside of the slide where the gas cylinder makes contact with slide (see pictures). At first I thought it to be powder discharge or carbon that one would expect might leak from the gas port, but the solvents and lubricants I use during cleaning do not reduce or remove.

    Appreciate any advice/ opinion you all my have. Is it common to see buildup at this location? Is it potentially a hazard or safety concern?

    Thanks,

    Gary

    Attached Files:

  3. JLA

    JLA Well-Known Member

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    Its just baked on carbon. Understand that the gasses directly behind the bullet are at around 35000 PSI in the .30 carb. Thats alot of pressure, which amounts to alot of heat. It will come off, but you will have to soak it overnight and use a pick to break it up.
  4. Jim K

    Jim K New Member

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    A sharpened broad blade screwdriver will take it off. Just don't dig into the metal, only into the carbon. That buildup is more than normal and may indicate a serious leak, but then I don't know how long it has been since the carbon was cleaned off. You might want to check the piston and piston nut and make sure they are correct and fitted properly.

    Jim
    Last edited: Jan 1, 2012
  5. gary.matcek

    gary.matcek Member

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  6. gary.matcek

    gary.matcek Member

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    JLA,

    Thanks

    Jim,

    I recall that I could see some threads of the gas piston nut extending out of the gas port. Should that nut be flush, all the way in with no threads visible?

    Gary
  7. StoneChimney

    StoneChimney New Member

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    What does the gas piston look like?
  8. Jim Hauff

    Jim Hauff New Member

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    Looks to me like very dense (graphitized) carbon build up. Try working on it with a dental pick - see if you can chip or lift some of it off the steel. Removing this stuff, if it is as I suspect, chemically, is difficult but can be done by getting something to penetrate under the build up - it occurs in very thin sheets and the carbon atoms have a high affinity for bonding with iron and with each other under high heat and pressure. Mechanical removal may be in order.
  9. gary.matcek

    gary.matcek Member

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    Thanks, Jim.

    StoneChimney asked me what the gas piston looked like, so I have posted pictures of same.

    Threads of the gas piston nut appear to extend out away from the gas port. Should that be flush, with no threads visible?

    Thanks,

    Gm

    Attached Files:

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