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Thread: AR15 headspace

  1. #1
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    Default AR15 headspace

    Hi all,

    I'm putting together an AR15 with a new LMT BCG and Krieger barrel, for giggles I decided to check headspace before putting everything else together. I stripped the bolt and re-assembled the carrier group and proceeded checking with the "GO" gauge. With light pressure, the bolt would only turn about 10 degrees and stop. I put several live rounds in from various mfgs and the bolt turned and locked on all of the rounds. Several questions:

    1. The barrel is chambered for 5.56, but the gauges are for .223. Is this what is causing this?

    2. Is this a big enough problem that I should send the barrel with bolt back to Krieger to get them to match the bolt to the barrel? Or is it just this tight because its a match barrel and will eventually wear in?

    From google searches on the subject, none with a solid answer, it appears that it is unusual to have, however, there is no risk of damaging anything. It would require more frequent cleaning and may not function reliably until it is worn in. Any opinions here?

    Thanks.

  2. #2
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    Default

    Are you sure the extractor was making it over the gauge?

  3. #3
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    Default

    Quote Originally Posted by RKG View Post
    Are you sure the extractor was making it over the gauge?
    Yes. I removed it and the ejector before trying.

  4. #4
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    Default

    I'm pretty sure there is a slight difference. The SAAMI Reference print says a the Go headspace dim. is 1.4636. Let me see if I can find the .gov print.

    I'm sure it's fine. Most ammo is not going to be made at the SAAMI max. Do you reload? If so make sure your die will size a case enough.

    B

  5. #5
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    Go here to www.AR15Barrels.com and look down the page at the Headspace Gauge Dimensions Comparisons.

    Whose gage are you using?

    B

  6. #6
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    Default

    Thanks for the link. Very informative. The gauge is made by Forster.

    It looks like the 5.56 chamber length is actually .0002" longer than the .223 chamber. I'm guessing it is only a fraction of the mfg. tolerance but is still not to my benefit.

    Looking a little more carefully at the paperwork that came with the GO gauge, it reads that it will check the rifle chamber to see that it will accept catridges made to the MAX spec. I'm interpreting this as it should be ok, but will require more cleaning and it probably will be picky about what I feed it.

    I do reload, just starting out with .223. I'll have a post about the dies in the reloading forum if I can't find it via search soon enough.

    Thanks!

  7. #7
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    Having tight headspace is not a bad thing if you are going to reload that brass. It will make it last a lot longer. I've had a couple of guns with pretty tight headspace and I never noticed any problems. As long as your ammo fits, and the sizing die can squeeze it down enough so that it will fit when you re ize it you should be fine.

    I can't imagine you are going to do mag dumps with a new Krieger or shoot 1500 rounds of Wolf steel case ammo between cleanings, so you should be fine.

    B

  8. #8
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    B-

    That's what I like to hear!

    With the cash I'm dumping into this, there will definitely be no mag dumps and I was planning to shoot mostly match ammo and reloaded ammo whenever I get the .223 sizing problem fixed.

    Thanks very much for your help here.

    -Kevin

  9. #9
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    If the chamber is too tight the gun will not function short strock or not eject. I have run into two tight chambered barrels in the last year. One from Shelin and one from AA. The one from AA was a Beowolf 50. I sent both these barrels back to the Mfg. to have them finish reamed because they were under waranty. If you have a problem you should do the same at least you should call Krieger and let them know your findings. They are best to guide you.

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