Results 1 to 9 of 9

Thread: Headspace

  1. #1
    Join Date
    Dec 2015
    Location
    The New World
    Posts
    593
    Feedback Score
    0

    Headspace

    When should headspace be checked and with which gauges, go, no go, field gauge?
    Big brother is watching...and listening.

  2. #2
    Join Date
    Jun 2006
    Posts
    3,865
    Feedback Score
    19 (100%)
    I spoke with IG on this early in the year and he advised to just go with a Field gauge, I use the Colt one fro Brownells. (1.4736)

    I would if replacing a bolt on a used upper
    Switching a bolt from another
    On a new build, maybe a GO as well just to make sure who ever made it will allow chambering and nothing excessive either.
    If having a high round count upper to insure it hasn't worn to the point of unsafe


    https://www.brownells.com/gunsmith-t...-prod6646.aspx
    GET IN YOUR BUBBLE!

  3. #3
    Join Date
    Jul 2010
    Posts
    4,382
    Feedback Score
    42 (100%)
    Quote Originally Posted by mark5pt56 View Post
    I spoke with IG on this early in the year and he advised to just go with a Field gauge, I use the Colt one fro Brownells. (1.4736)

    I would if replacing a bolt on a used upper
    Switching a bolt from another
    On a new build, maybe a GO as well just to make sure who ever made it will allow chambering and nothing excessive either.
    If having a high round count upper to insure it hasn't worn to the point of unsafe


    https://www.brownells.com/gunsmith-t...-prod6646.aspx
    Same here.

    If excessive headspace, first replace bolt assembly and then recheck. If headspace is not corrected, replace barrel assembly; then recheck with the original bolt to determine if the bolt is still good or if the bolt should be replaced also.
    E pluribus unum

  4. #4
    Join Date
    Dec 2015
    Location
    The New World
    Posts
    593
    Feedback Score
    0
    Quote Originally Posted by mark5pt56 View Post
    I spoke with IG on this early in the year and he advised to just go with a Field gauge, I use the Colt one fro Brownells. (1.4736)

    I would if replacing a bolt on a used upper
    Switching a bolt from another
    On a new build, maybe a GO as well just to make sure who ever made it will allow chambering and nothing excessive either.
    If having a high round count upper to insure it hasn't worn to the point of unsafe


    https://www.brownells.com/gunsmith-t...-prod6646.aspx
    On the field gauge you referenced from Brownells, does it work like a NO-GO gauge? Meaning the stripped bolt should not turn?
    Big brother is watching...and listening.

  5. #5
    Join Date
    Mar 2012
    Location
    Kansas
    Posts
    8,851
    Feedback Score
    1 (100%)
    Yes.

    Here is what the TM says: ETA - Change 4 Page 3-47

    6. Assemble charging handle assembly (4), bolt assembly, and key and bolt carrier assembly (5) into upper receiver assembly (6).

    7. Insert headspace gage (7) PN 7799734 in chamber. Important to note that the gag PN7799734 does not require removal of the ejector because the rim is relieved to allow the ejector to remain uncompressed

    For the purpose of this test "light finger pressure" is defined as 8 1/2 to 8 3/4 pounds.

    8. Check headspace by pressing key and bolt carrier assembly (5) and charging handleassembly (4) forward using light fingerpressure.

    9. Bolt should not rotate to locked position. Key and bolt carrier assembly (5) must protrude from rear of upper receiver assembly (6) for proper headspace. If excessive headspace,first replace old bolt assembly with an unused bolt assembly and then recheck.
    Last edited by 26 Inf; 11-09-19 at 20:45.
    Patriotism means to stand by the country. It does not mean to stand by the President... - Theodore Roosevelt, Lincoln and Free Speech, Metropolitan Magazine, Volume 47, Number 6, May 1918.

    To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public. Sedition, a Free Press and Personal Rule, The Kansas City Star, May 1918

  6. #6
    Join Date
    Mar 2015
    Posts
    879
    Feedback Score
    0
    If you do not have gauge, P/N 7799734, removal of the extractor may be required...

    For the AR type barrel, the primary use for the GO and NOGO gauge are at the factory, in conjunction with a gauge bolt, to insure that the barrel and barrel extension are properly assembled. If you are the type that cuts his/her own chambers, then a GO and NOGO are essential. Otherwise, just a FIELD is necessary to check for wear.

    Unless you have little confidence in you barrel or bolt manufacturer, not that there is anything wrong with that, it this case.

  7. #7
    Join Date
    Dec 2015
    Location
    The New World
    Posts
    593
    Feedback Score
    0
    Thanks!
    Big brother is watching...and listening.

  8. #8
    Join Date
    Sep 2008
    Posts
    1,109
    Feedback Score
    3 (100%)
    I'm astonished that no commercial gauge maker has made one with relief, so we don't have to remove the ejector.

    M4C machinists: why not buy some Colt ones and do the mod? I'd buy one if reasonably priced. I bet lots of other AR-heads would too.

  9. #9
    Join Date
    Mar 2015
    Posts
    879
    Feedback Score
    0
    Quote Originally Posted by Uni-Vibe View Post
    I'm astonished that no commercial gauge maker has made one with relief, so we don't have to remove the ejector.

    M4C machinists: why not buy some Colt ones and do the mod? I'd buy one if reasonably priced. I bet lots of other AR-heads would too.
    Because most head spacing is done by gunsmiths in incomplete barrels and unassembled bolts.

    The Army head space gauge (P/N 7799734) doesn't even have a extractor groove.

    Last edited by lysander; 11-10-19 at 11:18.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •