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Thread: Name & Use Of This Part Of Bolt?

  1. #1
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    Name & Use Of This Part Of Bolt?

    What is the name of the diagonal depression on these Colt bolts just behind the lugs?
    More importantly, what is the function of these depressions?
    (I understand that many FN bolts have a similar depression but with a semi-elliptical sort of shape.)
    Thanks.


  2. #2
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    I'm not sure of the specific name but I believe these are for debris clearance.

  3. #3
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    It's from the tool that cuts the chamfer on one side of the lugs.

  4. #4
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    More oddities noticed:

    1) Why are the letters "MPC" tilted on some bolts, but not others?

    2) Why is the raised ridge between the cam pin hole and the letters MPC apparently flutted on some bolts, but not on others?

  5. #5
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    Go ask your mother.

  6. #6
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    It's all magic.
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  7. #7
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    Not all of those look like Colt bolts...
    Last edited by MarkG; 08-28-10 at 01:02.

  8. #8
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    these are all machining slop, for lack of a better term. the "fluting" is just where the lug cutting tool grazed the rib.

    the stamps are in different spots because they're just wherever the stamper decided to stamp them

    there's no method to this madness

  9. #9
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    Poor tooling control on the CNC machine during lug cutting.

  10. #10
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    Quote Originally Posted by MK18Pilot View Post
    Not all of those look like Colt bolts...
    Which ones & why? To the untrained eye (meaning yours truly), they all look the same except for the one where the lug cuts extend back into the ring around the bolt body. I know zip about colt parts, so I'm curious what makes them different.

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