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hawk18hawk18 Senior MemberPosts: 742 Senior Member
I didn't want to high jack Uncle Festers thread, but, my question is:  When you guys are building uppers or swapping barrels or swapping bolts, do you use head space gauges?  I'm fixen to swap out the barrel and hand guard on an AR and have never done that before. 

Hawk

Replies

  • BigslugBigslug Senior Member Posts: 8,267 Senior Member
    edited March 2019 #2
    Only always.

    Headspace gauges confirm several things for you:

    1. The bolt and barrel will be compatible with each other.  You're usually OK using a new bolt and barrel from the same manufacturer, but everybody has a bad day from time to time, and if you're pairing an old of one with a new of another, it's anybody's guess.

    2. Whoever put the gun together did it right, at several points in the process.

    3. The gun will operate safely.  Excessive headspace in an AR can not only lead to the usual problems of case head separation, but also to primers popping out of pockets and rattling around inside the firearm, where they can jam up the works in several ways.

    To do it right, you need a set of three - properly from the same manufacturer, and you'll want to know going in if you're dealing with .223 or 5.56 chamber specs:

    1. Field.  This is the biggest, "gun is screwed up" gauge.  If your rifle can lock into battery with that, you've got problems.

    2. NO-GO .  Rifle ideally should not chamber this one, but not the end of the world if it does - so long as it does not also chamber the Field gauge.  Be aware that beyond here there be dragons  You'll have shorter brass life and have a higher risk of case head separations on multi-use brass.  Better to find a bolt/barrel combo that locks up properly.

    3. GO.  Basically a hardened steel dimensional copy of a live cartridge.
    WWJMBD?

    "Nothing is safe from stupid." - Zee
  • tennmiketennmike Senior Member Posts: 27,403 Senior Member
    Yes. GO and NO GO gauges are the tools that keep your handsome mug from being destroyed. And Bigslug covered the 'why' well. Checking headspace is 5 minutes and a few dollars well spent, and peace of mind is priceless on that first shot!
      I refuse to answer that question on the grounds that I don't know the answer”
    ― Douglas Adams
  • JayJay Senior Member Posts: 3,869 Senior Member
    I can't say it any better the Bigslug did.  I generally only use No-Go and Field.  Once those are checked, if it'll chamber a live round or a dummy made to correct specs, it's good to go.  I have seen several guns that will chamber a No-Go, but not Field.  In that case, I'll go with it and keep an eye on it.  If it ever chambers a Field, that's a definite stop and don't shoot that gun until it's figured out.  Sometimes just swapping bolts will get it where it needs to be.
  • hawk18hawk18 Senior Member Posts: 742 Senior Member
    Thanks guys. Info from people you trust seems better than that found on YouTube. 

    Next question:  I'm changing from an unfired .223 Rem bolt and barrel to an unfired 6 mm x 45. According to Pacific Tool and Gauge, the.223 Rem set will work for both cartridges. Do you feel this is correct. 

    Hawk
  • JasonMPDJasonMPD Senior Member Posts: 6,557 Senior Member
    hawk18 said:
    Thanks guys. Info from people you trust seems better than that found on YouTube. 

    Next question:  I'm changing from an unfired .223 Rem bolt and barrel to an unfired 6 mm x 45. According to Pacific Tool and Gauge, the.223 Rem set will work for both cartridges. Do you feel this is correct. 

    Hawk
    Someone who knows will say definitively, but if a cartridge regardless of caliber is identical dimensionally from mid-shoulder to base, they usually headspace identically and the parent cartridge gage would be appropriate. 
    “There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves.” – Will Rogers
  • JasonMPDJasonMPD Senior Member Posts: 6,557 Senior Member
    And if PTG says it’s good, it is. They aren’t mucking about. 
    “There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves.” – Will Rogers
  • tennmiketennmike Senior Member Posts: 27,403 Senior Member
    When buying headspace gauges, the manufacturers list all the cartridges that the particular headspace gauge can be used for. One gauge can be used to gauge several different ones using the same cartridge case with unaltered case shoulder.
      I refuse to answer that question on the grounds that I don't know the answer”
    ― Douglas Adams
  • BigslugBigslug Senior Member Posts: 8,267 Senior Member
    I don't know the 6x45, but have dealt with PTG on a number of things.  I'd take their word for it.
    WWJMBD?

    "Nothing is safe from stupid." - Zee
  • hawk18hawk18 Senior Member Posts: 742 Senior Member
    Thank you gentlemen. I see a set of gauges in my future. Funny thing is, PT&G is four or five miles from my house. I will drive by there tomorrow but will order it and have them ship it. The last time I dropped by and purchased a trigger guard, they had trouble dealing with a face to face transaction. 

    Hawk
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