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Mil-Spec vs.Commercial Spec...

Discussion in 'General Firearm Discussion' started by Poonaner, Jun 27, 2011.

  1. Poonaner

    Poonaner Olympia, WA Member

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    This might be a stupid question but whats the difference between Mil-Spec stocks & accessories and Commercial Spec stuff? And how do you know which one you need to have? I have a Bushmaster Superlight Carbine AR-15 and am looking for a Magpul stock for it but have no clue which I need...

    Thanks in advance for enlightening a noob like myself :thumbup:
     
  2. chizuck

    chizuck central Wa. Member

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    Does the end of the receiver extension have a slant or is it flat? If it is flat it is mil, and slanted is commercial.
     
  3. NoAim

    NoAim Hillsboro, OR Active Member

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  4. ikari2_2000

    ikari2_2000 Seattle, WA Member

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    In case you want to know why.

    MrCleanOK July 12, 2009, 10:39 AM

    Commercial tubes have cut threads, milspec tubes have rolled threads. This is why commercial tubes are thicker, folks. To get the same thread dimensions with cut threads, you have to have more material to start with. Rolled threads are stronger (increase in material's yield strength through plastic deformation), and have better fatigue life (sharp corners on cut threads serve as stress concentration points).
     
  5. madcratebuilder

    madcratebuilder Ardenwald, OR Well-Known Member

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    Your Bushmaster would have a commercial size RE from BM.

    magpulbuffertube.jpg

    True mil-spec RE's are forged 7075, some after market mil-spec RE's are 6061 and extruded. Mil-spec or commercial is fine just don't mix the parts.

    This is generally the rule but there are a few exceptions.
     
  6. DoubleTapDrew

    DoubleTapDrew Oregon Well-Known Member

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    +1 I changed out an old Oly extension to install a Vltor stock and don't recall the commercial tube having a slant.
     
  7. Poonaner

    Poonaner Olympia, WA Member

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  8. Poonaner

    Poonaner Olympia, WA Member

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    i haven't taken off the stock yet, the threads are visible when i extend out the factory 6 position stock.
     
  9. NoAim

    NoAim Hillsboro, OR Active Member

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    Take a pair of calipers and measure the diameter. Surest way to tell.
     
  10. DoubleTapDrew

    DoubleTapDrew Oregon Well-Known Member

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    if you want to check the back end grab the adjustment latch, pull it down (away from the stock) in both the front and back, it should slide off.
     
  11. Poonaner

    Poonaner Olympia, WA Member

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    no calipers, the end of the tube is flat, not angled.
     
  12. Buddhalux

    Buddhalux Hillsboro, Oregon Active Member

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    On Mil spec tubes the threads extend outside of the tube so that the threads look larger than the tube itself. On commercial tubes the threads look flat on the outside on the tube.
     
  13. Poonaner

    Poonaner Olympia, WA Member

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    threads are flat with the tube. maybe i should just pick up some calipers.