Annoying Headspace Gauges AR-15

[Discogodfather]

Headspace gauges are like opinions, everyone has a different one. Don't ask me how many different definitions of GO / NOGO there are. If you think military and civilian is the difference I have seen a few that are completely different dimensions and considered to be military or civilian.

I recently got a set of Forester gauges (labeled .223) and they read:

GO 1.4636
NOGO 1.4666
FIELD 1.4696

So I pulled out 4 different barrels from BRO, Spikes, White Oak, and Model 1. I checked all of them and they all close on the 1.4666 NOGO. I was besides myself thinking they where all out (one is brand new) but came to my senses and concluded they all can't be out of spec. I tried a different bolt to make sure. Followed all proper procedure with the ejector/extractor removed.

3 of my barrels are 5.56 and one is a Wylde, so I thought maybe the .223 was a different size than the 5.56. It's not! 5.56/.223 gauges are the same.

So what is the point of a 1.466 NOGO gauge? All the civ/military gauges I see from other manufacturers are in the 1.47+ range. What is Forester thinking?

None of the barrels would close on the FIELD 1.4696, which is also alot smaller than the 1.4736 military FIELD.

Am I making any sense?

[tujungatoes]

Yes you're making sense. You have to keep in mind that these are 5.56 barrels for semi-auto rifles. They are cut a little "roomy" to ensure reliable feeding and extraction. They're not going to be as tight as the chamber in a bench rest gun. If you look at specs on 5.56 gauges you'll see they don't have go/nogo/field. Just 2 min/max and the dimensions are different.

[kendog4570]

223 and 5.56 have the same industry standard minimum and maximum headspace dimension. Minimum is 1.4636" and max is 1.4736". To simplify it a little, SAAMI works of the smaller side, and NATO the larger, but they both have the same minimum and maximum for the parent caliber, which is now known as .223 Remington.
If your barrels are chambered for the NATO round, then they probably will close an SAAMI no-go's.

[dankmin]

I wrote an email to forster regarding my AR 15 just a couple weeks back and this is what i received:

"Thanks for contacting us. The techs have suggested you start with a 223 GO gage and a 223 FIELD gage. If the FIELD gage ever closes in your AR15, you would then need to check it with a 5.56 NATO MAXIMUM gage."

If i remember right, the dimensions of the 223 Go and the 5.56 minimum gauges are the same.

Go:1.4636
223 Field: 1.4696
5.56 Max: 1.4736

[Discogodfather]

"Thanks for contacting us. The techs have suggested you start with a 223 GO gage and a 223 FIELD gage. If the FIELD gage ever closes in your AR15, you would then need to check it with a 5.56 NATO MAXIMUM gage."

That restores my sanity, thanks for the responses. Sounds like the Forester NOGO .223 gauge should be re-titled the "Champion Super Tight Benchrest" NOGO gauge.

Wow, wouldn't it be a lot easier to just call these things as dimensions and just get ride of the go-go-no-go-no silliness.

[kcstott]

AR15barrels has a very nice write up on all the variations of gages involved between 5.56 and .223
And even though they are dimensionally identical in most areas the 5.56 has radius call out on shoulder, a longer throat and a higher operating pressure.

[ar15barrels]

https://www.ar15barrels.com/data/headspace.pdf

The major difference between 5.56 and 223 is that the 5.56 no-go and field are about 0.003" longer.
This effectively makes a 223 field gauge into a 5.56 no-go gauge.