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Thread: AR-15 GO/ NOGO Gauges

  1. #1
    Business Member True North Arms Corp's Avatar
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    AR-15 GO/ NOGO Gauges

    We've built up a nice selection of Go/Nogo gauges for AR-15 builds.

    For those unaware these are basically dummy rounds made from tool steel and precisely sized to fit in the chamber and confirm you have the right headspace. This is important to check when assembling an AR (or SLR, WK-180c, or BCL102) Upper, because if the headspace is too tight the rounds won't chamber (or they chamber wayy too tight), if too loose then your case can rupture or worse.

    How to use -- first make sure your chamber and bolt are clean, then drop the GO gauge in the chamber, try to close the bolt, is should close easily. Eject and then try the same with the NOGO gauge, the bolt should not close. If it closes on both gauges, you have too much headspace, if it won't close on either gauge, then you don't have enough headspace and it's back to the bench or smith for adjustments.

    Our gauges are made by a precision tool shop for us to SAAMI specs and laser-etched with the chamber size and "go" or "no-go" so there's no mistaking what's what.

    We realize some folks are reluctant to buy an expensive tool to use it only once or twice so we offer a rental program. Simply buy the gauges normally, use them and ship them back and we will refund you the purchase price less a $20 rental fee per pair.

    At the time of writing we've got the following GO NOGO gauges in stock:
    • 556 Nato
    • 223 Rem
    • 300 BLK (AAC)
    • 204 Ruger
    • 224 Valkrie
    • 6.8 SPC II
    • 223 Wylde
    • 6.5 Grendel
    • 7.62x39

    not here yet but on the way:
    • 6x45
    • 277 Wolverine


    Last edited by True North Arms Corp; 10-25-2018 at 04:04 PM.
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  2. #2
    CGN frequent flyer KND's Avatar
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    Wow ! Those are nice.

    How about a Match headspace set for 308 win and 6.5 creedmoore ? Thanks.

  3. #3
    CGN frequent flyer CHEMMY's Avatar
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    This is great! Especially for those of us who might only make a build or 2 every couple years. The rental program is a great idea.
    ̿' ̿'\̵͇̿̿\з=(•̪●)=ε/̵͇̿̿/'̿''̿ ̿ If you always do what you've always done, you'll always get what you've always got. ̿' ̿'\̵͇̿̿\з=(•̪●)=ε/̵͇̿̿/'̿''̿ ̿

  4. #4
    CGN Regular tony9000's Avatar
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    can we keep guages, if we dont want to rent?
    Everything i post, or ever posted, is for entertainment value. Draw your own conclusions, and always seek legal advice.

  5. #5
    Super GunNutz stevey3737's Avatar
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    Hi there so if we have too tight with the ar barrels i assume the only way to adjust is machining the barrels? Or are there shim packs for the barrels?

  6. #6
    Business Member True North Arms Corp's Avatar
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    Quote Originally Posted by KND View Post
    Wow ! Those are nice.

    How about a Match headspace set for 308 win and 6.5 creedmoore ? Thanks.
    We can make Match sets as a special order. Let's say a set of 11 gauges in 1 thou increments for $499, lead time 2-3 months.
    True North Arms Corp.
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  7. #7
    Business Member True North Arms Corp's Avatar
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    Quote Originally Posted by tony9000 View Post
    can we keep guages, if we dont want to rent?
    yes of course, simply buy and keep
    True North Arms Corp.
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  8. #8
    Business Member True North Arms Corp's Avatar
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    Quote Originally Posted by stevey3737 View Post
    Hi there so if we have too tight with the ar barrels i assume the only way to adjust is machining the barrels? Or are there shim packs for the barrels?
    Shimming isn't practical, the headspace is a matter of how the bolt, barrel extension, and chamber all stack up.

    if I won't close on the GO gauge, I would remove the ejector and extractor then try again. Also ensure the chamber and bolt are clean.

    If it still won't close on the GO gauge, then either the chamber needs to be reamed or the bolt lugs machined slightly.

    If other bolts are handy it will be wise to test those, to determine if the issue is the chamber or the bolt. (If other bolts fit fine, then the problem is likely that bolt, and you'd stone or machine the rear of the bolt lugs in small increments till it closes well.) If other bolts don't fit either, then likely the chamber needs to be reamed slightly. If these are factory new parts, contact the retailer or manufacturer, it's their problem. If it's a used gun then you're on your own / need a gunsmith or buy a new bolt and/or barrel.

    A bolt that closes but slightly tight is not necessarily a problem, as new parts can have surface roughness that gets broken in and loosened up after shooting it. Remember what Ghandi once said -- first time tight, second time alright

    If the bolt closes on a NO-GO gauge (i.e. headspace is too long), then the chamber is too deep and/or the bolt lugs are too short, so this can't be resolved without replacing one or both parts. Test other bolts to determine if the issue is the bolt or the barrel.

    Another option is removing and re-installing the barrel extension, but at that point might as well buy a new barrel unless it's a really special barrel
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  9. #9
    CGN Ultra frequent flyer tharkhold's Avatar
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    That's a great initiative.

    That's also why I started a "head for coffee" thing in the EE for the Ottawa region. I've got 556 and 308 gauges, and willing to meet up with someone for a coffee and check their headspace
    'nada

  10. #10
    CGN Regular AMET's Avatar
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    would the .223 Wylde GO gauge be the same as the 223/556?
    "This year will go down in history. For the first time, a civilized nation has full gun registration! Our streets will be safer, our police more efficient, and the world will follow our lead into the future."
    Adolf Hitler, 1935

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