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Thread: Name & Use Of This Part Of Bolt?

  1. #51
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    Quote Originally Posted by bo-hoss View Post
    These are the bolts we use at work. No cuts around the lugs.

    The reason there are no cuts on those bolts you use is because the lug roots are smaller in diameter, making room for the cutter that cut the leading edge chamber on each lug.

    If you took any of the other bolts in this thread and reduced the diameter of the lug roots, those diagonal cuts would mostly dissappear.
    Randall Rausch
    AR15 Barrel Guru
    California Precision Rifle Club founding member

  2. #52
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    Quote Originally Posted by patrick sweeney View Post
    But if the drawings, inspection standards and mechanical function do not require it, a manufacturer is not going to lose much sleep over cosmetic differences.



    What he said.






    That second pic has been in that folder for a long time, funny how the same questions come 'round in the long view.

  3. #53
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    Quote Originally Posted by Tweak View Post
    What he said.






    That second pic has been in that folder for a long time, funny how the same questions come 'round in the long view.
    Tweak,
    Do you by chance have any drawings covering other bolt dimensions/tolerances such as:

    Bolt bearing band width/diameter/placement.
    Bolt lug length/width.
    Bolt face/cartridge seat.
    Cam pin hole.
    Gas ring channel.
    Extractor channel.

    Ive seen variations in the above and no solid +/- specs to reference beyond averages from actual bolt measurements Ive had in hand.
    Glock Certified Armorer
    Armed Protective Services II

  4. #54
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    The semi circular marks are a residue of the machining operation required to provide the cam in chamfer on the lead side of the bolt lugs. The bolt, being ground after heat treatment will display varying depths but it is typical for a witness to remain. It is not desirable for them to be removed completely as the point is a junction of three such fillet radii. They are typically refered to as deer feet marks. The short cuts shown latter in the thread are an alternative method of producing the same feature but were not used for long as the base radius is difficult to control in respect to tooling wear.

    The bolts in the first picture are unusual. The marking residual in the front bearing surface denotes that these are pot broached. The marking should not be present in a finished bolt. Pot broaching is not a very common production route but has been used for bolt production. More typically the lug forms are milled with a form cutter and with the advent of more complex machines it is not unusual to pinch mill the lug profiles.

    The use of cam in surfaces on the bolt are matched with equal chamfers that exist on the inside edges of the barrel extension. These are not easily machined and are more typically coined. In correctly made extensions the cam in is present together with an inner edge chamfer after final machining which again is performed after heat treatment.

  5. #55
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    Out of curiosity, anybody have an SR15 bolt in hand for comparison?

  6. #56
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    Quote Originally Posted by Bill Alexander View Post
    In correctly made extensions the cam in is present together with an inner edge chamfer after final machining which again is performed after heat treatment.
    This one is too big for a pic here so here's the address.

    Barrel extension print

  7. #57
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    Todd answered this question almost 2 years ago when the thread was posted.....
    Stick


    Board policy mandates I state that I shoot for BCM. I have also done work for 200 or so manufacturers within the firearm community. I am prior service, a full time LEO, firearm instructor, armorer, TL, martial arts instructor, and all around good guy.

    I also shoot and write for various publications. Let me know if you know cool secrets or have toys worthy of an article...


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  8. #58
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    And after all this time, the question still is - does HPT/MP make for a better bolt........?

    FWIW - my FN and DD bolts are not similar, & glad to see I'm not the only OCD BCG nut out there.
    Per Ardua ad Astra.
    STS - gone but not forgotten.

  9. #59
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    Quote Originally Posted by Stickman View Post
    Todd answered this question almost 2 years ago when the thread was posted.....
    True. However, Bill Alexanders dropped a nugget in here that I enjoyed reading...
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    Quote Originally Posted by okie john View Post
    Posers buy guns. Shooters buy ammo.
    Okie John

  10. #60
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    Quote Originally Posted by Stickman View Post
    Todd answered this question almost 2 years ago when the thread was posted.....
    True. However, Bill Alexanders dropped a nugget in here that I enjoyed reading...
    www.thealaskalife.com www.facebook.com/thealaskalife
    Quote Originally Posted by okie john View Post
    Posers buy guns. Shooters buy ammo.
    Okie John

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