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  • Do you check headspace on your builds?

    Posted by brian on March 15, 2022 at 3:12 am

    Getting ready to finish a build this week with the barrel and upper. I know that it’s recommended you get go/no go gauges and verify your headspace but is it really necessary? If it’s off – is there anything I can even do short of buying a new barrel?

    For info – Im using a faxon barrel on an Aero m15 upper.

    brian replied 10 months, 4 weeks ago 2 Members · 1 Reply
  • 1 Reply
  • Traditional-Bat3508

    March 15, 2022 at 3:12 am

    No. I would consider it a troubleshooting process that is usually unnecessary

  • ncreddit704

    March 15, 2022 at 3:12 am

    I’ve never

  • Trollygag

    March 15, 2022 at 3:12 am

    >I know that it’s recommended you get go/no go gauges and verify your headspace but is it really necessary?

    If you do, risk falling into the same trap that perpetuates this idea – the confusion between what the gauges mean and what headspace is valid.

    There appears to be a lot of confusion point, so let me break it down again and explain from the top what headspace gauges are, what their function is, and why.

    Gauges are a way to check a dimension on one axis of a weird shape. Headspace is the shape of the chamber from the bolt face to the datum line.

    Headspace range is the valid dimension for a specification for a chamber that allows ammo to fit and still be supported by the chamber.

    If the ammo doesn’t fit:

    1. If it is too short, the rifle will not chamber and the brass may get stuck.
    2. If it is too long, the case may stretch a lot or even crack, causing gas to blow-by the case, which can cause erosion in the chamber, fouling, gas-in-face from the gas relief ports on the bolt carrier, popped primers, broken extractors, and other annoying things like case pieces stuck in the chamber.

    There are differing gauges used to signify different things.

    * Go Gauge – this is the gauge a bolt is supposed to close on signifying the start of some headspace range.
    * Min gauge – this is the gauge a bolt is supposed to close on specifying the minimum headspace range for the cartridge.
    * No-Go gauge – this is a gauge a bolt is not supposed to close on for the end of some headspace range. This is almost always 3-4 thou from a go-gauge.
    * Field gauge – this is a gauge a bolt is not supposed to close on that specifies when the rifle needs replacement parts. This is almost always 3-thou from a No-go gauge.
    * Max gauge – this is a gauge the bolt is not supposed to close on that specifies the maximum headspace range for the cartridge at which point you should replace parts.

    Okay – a lot of that sounds similar, and that’s because there is some nuance.

    You may ask yourself “if you aren’t supposed to exceed the no-go, then why is there a field gauge?” Well, that is because there are 2 different use cases for headspace gauges. 1 is making barrels – the target range you are trying to hit, 2 is for diagnostics – figuring out when barrels need to be replaced or when there is a problem.

    Min/Max set absolute limits for diagnostics, Go/No-Go are a more general tool-set for making barrels, and a Field gauge is a diagnostic gauge.

    Standards bodies set headspace ranges which CAN (but don’t have to), make Go/No-Go/Field headspace the minimums and maximums of the cartridge.

    Some of this is based off use case, some of it based off the standards body, and some of it is based off practical considerations.

    ##Use case 1: Barrel making

    When barrels are made, they almost always use a Go/No-Go system of some dimension. The barrel maker decides on what headspace range they want to make barrels to and they order gauges to their own dimensions.

    This could be a 3-thou range, it could be a 4-thou range, it could line up to a SAAMI or CIP published range, or it could line up to some other range the barrel maker wants to hold to.

    For example, some custom barrel makers hold to 1 thou on headspace using custom made Go/No-go gauges or shimming a go-gauge.

    On ARs, barrels are often made using a test bolt set to some minimum tolerance and with a tighter chamber against that minimum tolerance so that any sloppy bolt you get will still fall withing 5.56 NATO’s huge headspace range of 0.010″.

    ##Use case 2: Diagnostics

    So as you see above, there’s a problem.

    Go/No-Go is a tight headspace range but the cartridge has a large headspace range to account for bolts not all being headspace together with the chamber.

    If chambers are made to the tight range but you don’t have a bolt as tight as the barrel-maker’s test bolt, then you have a good chance of failing a No-Go test that was used to set the chamber headspace.

    But that is OKAY. That is not what those gauges are supposed to be used for to begin with.

    For diagnostics, you should use a set of gauges designed for diagnostics. For 5.56 NATO, that is Min/Max. For SAAMI .223 Rem, that is Go/Field. Those are the chamber/bolt limits for the cartridge.

    You should NOT fail a Min or a Max test. That is indicative for parts defects. It is NORMAL to fail a No-Go gauge test with an AR-15 because there is no standard for a No-Go in an AR-15 and most No-Go gauges on the market do not cover more than 1/3rd of the valid headspace range.

    But that confusion is the root of why so many people freak out about headspace – they use the incorrect gauge to perform an invalid test, and then based on that invalid test result they spread the word that this can be an issue. Chicken little, the sky is falling.

    In reality, their headspace was PROBABLY perfectly fine all along. They would have found this out using the correct diagnostic gauges.

    ## But what about .223 Wylde?

    This gets weird. .223 Wylde has no published valid headspace range because it is effectively a wildcat chamber for 5.56 NATO. At its root, it is a 5.56 NATO chamber with a .223 Rem radially cut throat.

    Should you hold it to 5.56 NATO chamber specs or .223 Rem chamber specs? Nobody has authority to say until a standards body steps in.

  • RennBaer

    March 15, 2022 at 3:12 am

    I do. It’s piece of mind. Before swapping barrels, you can try swapping bolts. The tolerances on both contribute to your overall headspace.

  • HugoStiglitz_JR

    March 15, 2022 at 3:12 am

    I prefer the ol’ ten foot string on the trigger method for the first 5 rounds

  • Commandd0g

    March 15, 2022 at 3:12 am

    Every build, i have had barrels close on a nogo

  • russ257

    March 15, 2022 at 3:12 am

    I got a set of gauges. I check my builds. It’s for peace of mind.

  • Phantom_spook

    March 15, 2022 at 3:12 am