Quantcast
  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

AR 15 headspace

Discussion in 'Gunsmithing and Repairs' started by jelenko, Feb 17, 2012.

Thread Status:
Not open for further replies.
  1. jelenko

    jelenko Member

    Joined:
    Sep 5, 2011
    Messages:
    47
    I just rebarreled by AR 15. The fired cases are coming out 3-5 thousands larger than the earlier barrel.
    The bolt is the same.

    That means the chamber in the new barrel is 3-5 thousands larger than the previous one - yes?
     
  2. dprice3844444

    dprice3844444 member

    Joined:
    Feb 26, 2011
    Messages:
    4,264
    Location:
    se fla i love claymores 01/sot
    change bolt face
     
  3. rcmodel

    rcmodel Member in memoriam

    Joined:
    Sep 17, 2007
    Messages:
    59,082
    Location:
    Eastern KS
    Larger in diameter?
    Or longer headspace?

    If larger in dia, you have a looser chamber in the new barrel.
    If longer in length to the shoulder, you have more headspace in the new barrel.

    Did you check the set-up with GO and NO GO headspace gages when you put it together??

    rc
     
  4. jelenko

    jelenko Member

    Joined:
    Sep 5, 2011
    Messages:
    47
    It's longer - checked with RCBS precision mic.

    The fired cases are coming out +2 to +4 on the mic.
    Fired cases from the previous barrel [with the same bolt] came out - 1.

    I'm not too concerned since I resize the cases to ~ -2 thousands from the fired case size.

    I just wanted to make sure I've got it right that it's the new chamber that changed and not some way that the bolt was locking up in the barrel extension.
     
  5. xfyrfiter

    xfyrfiter Member

    Joined:
    Mar 17, 2010
    Messages:
    726
    Location:
    NW New Mexico
    Is the bolt new also? If not then you really should have the headspace gauged with go-no-go gauges, if it is a new bolt you should be ok but I would check anyway just for safety sake. A ka-boom next to your face is just not very pleasant.
     
  6. rcmodel

    rcmodel Member in memoriam

    Joined:
    Sep 17, 2007
    Messages:
    59,082
    Location:
    Eastern KS
    I'd be in favor of putting a new bolt in it to go with the new receiver extension.
    First, the wear pattern on the old locking lugs are not going to match the lugs in the new barrel extension.

    And by the time an AR needs a new barrel, it needs a new bolt too.

    Just a matter of time until it cracks a lug.
    Or breaks in two at the cam pin hole.

    Then you got a real problem to deal with.

    rc
     
  7. rskent

    rskent Member

    Joined:
    May 28, 2006
    Messages:
    1,347
    Location:
    The land of blue sky and sunshine
    Good advice – Most people I know keep the bolt with the barrel. When you change barrels
    you change bolts. When you put the barrel on another gun or sell it the bolt goes with it.
    Steve
     
  8. jelenko

    jelenko Member

    Joined:
    Sep 5, 2011
    Messages:
    47
    Hmmm. I change barrels about every 3-4 thousand rounds. The bolt has been in two previous barrels - but it has only about 6000 rounds through it.
    Are you really saying that a bolt only lasts about 4 thousand rounds?
     
  9. rbernie
    • Contributing Member

    rbernie Member

    Joined:
    Jan 21, 2004
    Messages:
    20,450
    Location:
    Norra Texas
    We had a recent thread on this:

    http://www.thehighroad.org/showthread.php?t=644284

    Considering that the bolt is a $70 part, it's probably wise to replace it with each new barrel from a cracking perspective. I was always taught to replace it with each new barrel from a wear/headspace perspective.
     
  10. Taurus 617 CCW

    Taurus 617 CCW Member

    Joined:
    May 25, 2003
    Messages:
    1,596
    Location:
    Northern Idaho
    Take it to a shop that has a set of headspace gages and have them verify the headspace. If you replace the bolt, have the headspace verified also.
     
  11. jelenko

    jelenko Member

    Joined:
    Sep 5, 2011
    Messages:
    47
    Ok. Changed the bolt, no change in size of fired brass.
    Since the fired brass all is well within SAMMI specs [as measured by the RCBS precision mic], I'm not concerned about headspace.

    If we could return to the original question. Given that the bolt is the same, if the brass comes out longer, it must be the chamber in the new barrel - yes?
     
  12. rcmodel

    rcmodel Member in memoriam

    Joined:
    Sep 17, 2007
    Messages:
    59,082
    Location:
    Eastern KS
    Yes.

    rc
     
  13. Jim Watson

    Jim Watson Member

    Joined:
    Dec 24, 2002
    Messages:
    21,970
    There was a guy here who felt similar anxiety when his fired cases showed a few thou longer in the RCBS gadget than he liked. The rifle was brilliantly accurate, much better than I would have expected out of a 3-gun AR, but he could not stand it and pressured the company for a new barrel. He got one with no excess headspace but it was not as accurate as the slightly sloppy original. Oh, well.
     
  14. jelenko

    jelenko Member

    Joined:
    Sep 5, 2011
    Messages:
    47
    Thanks!
     
Thread Status:
Not open for further replies.

Share This Page