Headspace

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  • 65Whelen
    Warrior
    • Sep 2014
    • 671

    Headspace

    Is there a way to check headspace without a set of Go/No-Go Gauges?

    Would using a depth micrometer and measuring from the rear of the barrel extension to the base of an installed cartridge be valid? If so what is the dimension and tolerance +/-?

    In the past I've cut chambers for bolt guns but never for an AR. For the AR, is the barrel extension on the barrel when cutting the chamber? Or, is the chamber cut and then the extension installed?
  • Adam Lilja
    Warrior
    • Dec 2013
    • 267

    #2
    The chamber is cut and then extension installed. It is nearly impossible to measure it w/o gauges and a bolt as you need the distance from the inside of the lugs to the case head.

    Comment

    • 65Whelen
      Warrior
      • Sep 2014
      • 671

      #3
      OK, thanks.

      Comment

      • sneaky one
        Chieftain
        • Mar 2011
        • 3077

        #4
        If you use the upper rec. frontal squaring tool -cutter in your AR- even if you take off only a small amount- you change the headspacing- if the unit was not squared in advance for you- what is the outcome? Hmmm. just a thought here- I don't think it's a game changer- all my 5.56 bolts fit just fine to a many different bbl. extensions- bbls.

        Grendel units are fine also- ... must be okay. Thoughts from Adam?

        Comment

        • NugginFutz
          Chieftain
          • Aug 2013
          • 2622

          #5
          I don't agree with that, s1, since the bolt is still indexed off the barrel lugs, which haven't changed from lapping an upper. Lapping the upper cleans up the interface between the barrel extension and upper. Bolt interface is not in play, here.
          If it's true that we are here to help others, then what exactly are the others here for?

          Comment

          • Wheelhorse
            Warrior
            • May 2014
            • 225

            #6
            Originally posted by NugginFutz View Post
            I don't agree with that, s1, since the bolt is still indexed off the barrel lugs, which haven't changed from lapping an upper. Lapping the upper cleans up the interface between the barrel extension and upper. Bolt interface is not in play, here.
            Yep, that's the way I have it figured too.

            Comment

            • Adam Lilja
              Warrior
              • Dec 2013
              • 267

              #7
              Originally posted by sneaky one View Post
              If you use the upper rec. frontal squaring tool -cutter in your AR- even if you take off only a small amount- you change the headspacing- if the unit was not squared in advance for you- what is the outcome? Hmmm. just a thought here- I don't think it's a game changer- all my 5.56 bolts fit just fine to a many different bbl. extensions- bbls.

              Grendel units are fine also- ... must be okay. Thoughts from Adam?
              Na you have a little bit of room to play because the bolt is not 'bottomed out' when it hits the case head. Its got room to float.

              Comment

              • sneaky one
                Chieftain
                • Mar 2011
                • 3077

                #8
                Right Adam- I was over thinking this. The locator pin is a constant also, right?

                Comment

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