Go No Go Gauge 5.56 Necessary?

When building an AR15, many builders ask if Go No Go gauge is required to install the barrel. The headspace is the space where the bullet fits in the chamber. If it's not right, the gun might not chamber the round properly, which can lead to malfunctions or accuracy issues. 

There are three main gauges used to check headspace:

  • Go gauge
  • No-go gauge
  • Field gauge

The go gauge checks if the chamber is long enough. The bolt should touch the go gauge, and there should still be some room. Some have a notch for the extractor, but if you're using the gauges, remove the extractor to avoid any pressure.

no go gauge ar15

The no-go gauge checks if the chamber is short enough. There's a specific length the chamber should be. If you compare a go and a no-go gauge, they're about six-thousandths of an inch different. They quickly show if the chamber is the right length.

Go and No Go Gauges

Tips For Checking AR15 Headspace

While most barrels and BCGs can be used together, but some may have that slight tolerance differences.

  • Always check headspace after making or changing major parts like the barrel or bolt carrier group.
  • Use good gauges. They usually cost between $60 and $80.
  • Keep the gauges intact so they provides precise measurement
  • Use the right tools. A bench block, punches, and needle-nose pliers are good choices.
  • If the check fails, don't shoot the rifle. Test a new bolt or barrel to find the issue.
  • Never miss this step. Quality parts usually pass, but it's risky to skip the check.

How Often To Check Headspace Tolerance

Check the headspace often for safety. Do this when you build a new rifle, switch barrels, or change the carrier group. This ensures the gun functions correctly.

If not checked, the rifle might malfunction. Problems can be case splits, primer issues, or the gun not firing or ejecting. The headspace varies with different cartridges. Always check it after any changes.

Problems With The Ammo

no go gauge

If the barrel and the BCG are working fine, the issue might be with the brass. For those who reload and reuse brass, always check that the brass length and bullet seating depth are correct.

To test, just place the cartridge into the case length headspace gauge. If it fits smoothly or sticks out, you'll know.

You don't really need a case gauge for this because your gun's chamber is the best tester. Create a few test rounds without any powder or primer. If they fit well in the chamber, come out smoothly, and can be extracted and ejected, then your sizing die is good.

Secondly, the gauge can help check if the case length is right and if it needs trimming. Instead of a gauge, I use a caliper set slightly below the maximum length. I then slide each case through. If a case doesn't fit, it needs trimming. If it fits, no trimming is needed.

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