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Posted: 3/27/2026 8:20:24 PM EDT
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Hi, I built a Aero Precision Upper/Lower 7.5inch 223 Wylde. So I borrowed a Go/No Go 556 gauge from a friend and checked and it did not pass. I got to thinking about it and thought about that the .223 should not be checked with a 556 gauge correct? Maybe I was a Dummy for not thinking about this at 1st. Just for the hell of it I tired 2 other different BGC's one from another 556 Aero P AR15, and one from my Colt LE6920. The other Aero P did not pass either. The Colt Bolt did pass. My thought is I need to get a 223 Gauge correct and check? So if I get the 223 Gauge and still don't pass then I need a new Bolt (Extractor insert) right? Please be patience with me as I am not new to AR15's, but am just learning about Building and want to do it the 100% correct way. Also what would be a good go to Go/No go 223 gauge to get from say Amazon? Other question is? If I have to get a whole new BGC, or Bolt insert Extractor? What would be recommended as a good one at a good value? Not el cheapo, but best bang for the buck? As much help as some some can give would be appreciated as I am still learning. Thanks! |
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All about the leade of the throat, with 223 the shortest, next the Wylde slight longer, then Nato being the longest of leade. Regarding chamber case width to barrel shoulder and last of actual case to end cut case neck cut, all the same.  So question comes down to what test gauge in play, hence are you just checking from bolt face to chamber case shoulder, or is the gauge in play checking the leade cut as well? Lastly, when checking head space, best to remove the ejector from the bolt, so our not fighting it on the test fit head spacing test, and maybe check the i.d, of the barrel extension lugs, with a bur that is causing true read problems as well. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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The lengths of headspace gauges made by different manufacturers and sold as 5.56 are not all the same. It is easier for me just to know that there is a minimum length, a maximum length, and all lengths between the two. If I wanted a gauge to measure the shortest length, I would look that length up and buy one advertised as that length from a reputable dealer. Here is some SAAMI info: https://saami.org/wp-content/uploads/2026/02/SAAMI-Z299.4-CFR-2025-Centerfire-Rifle-Approved-2-10-2025-2026-02-13.pdf Here is some FAQ's on their sight. One explains about the go, no-go, and field terms and a close read will reveal why the lengths might vary on a gauge of the same called out use being different between manufacturers. https://saami.org/faqs/#1622648797091-fd1263a1-69ea It would be less confusing if a Go, No-Go, and Field gauge for a caliber was were or had to be the same length for the type gauge but they don't. |
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Originally Posted By Maka15: So I borrowed a Go/No Go 556 gauge from a friend and checked and it did not pass. What do you mean "did not pass"? Closed on the No Go? Or did not close on the GO? Regardless of gage brand or caliber 223/5.56, it is still the same chamber dimension: bolt face to middle of shoulder. As mentioned above, the difference is leade/throat, which is not measured by the gage. |
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Not closing on the "Go" gage can be common on AR10/LR308 builds, but quite rare in AR15 since the standards have been set in stone for years. I have more faith in correct bolt dimensions and suspect the barrel/barrel extension is out of spec. Have you contacted the barrel manufacturer or vendor that sold it? |
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Originally Posted By smoothy8500: Not closing on the "Go" gage can be common on AR10/LR308 builds, but quite rare in AR15 since the standards have been set in stone for years. I have more faith in correct bolt dimensions and suspect the barrel/barrel extension is out of spec. Have you contacted the barrel manufacturer or vendor that sold it? AR in 308, is complete different ball game, since you have the Armalite platform, then the stoner/DPMS platform, and if are swapping barrels and bolts from the two different platforms, your head spacing is going to be all over the map. Hell, just to point out, on the armilite carrier, is slot for the hammer is much narrower, and if your trying to use a wider Stoner/DPMS hammer with that carrier, going to have problems as well. As for back in 223, all are same/same, so if you have problems, then something not up to spec (bolt or chamber). And again, in 223, face of bolt, bolt lugs locking into barrel extension, and distance from the bolt face to shoulders and to last of chamber next cut, all the same/same for spec if correct. Its just the difference in leade of each different type of chamber alone. The nato allow for more free jump of bullet, allows for more slight reduction in pressure during the fire forming off the case to chamber, were as Nato ammo in tight 223 chamber where the bullet may be slightly embedding on load, can cause over pressure at fire forming short stroking isntead. Lastly, and going to bring this up, some barrel manufacturers produced barrels on the tighter chamber cross wall section to try to promote accuracy, while it could back fire with reliability of the rifle to cycle correctly, since this increased ammo working pressure at firing forming instead. Case and point, Bushmaster tried this trick, but LEO where having reliability of cycling problems with the rigs having the chambers too tight, and got to the point that departments where veering away from buying from that manufacturer at one point. Also, since the shorter the barrel, the more violently the unlock with higher residual pressures at unlock, and in some SBR barrel chambers, cross wall dimensions being on the looser side, promote more cycling reliability in the rigs. Note, not talking a great deal, but more of simple chamber polish increase range instead. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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