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Why do I need headspace gauges for an AR build? Login/Join 
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I'm learning more and more about these builds as I go. I got a complete upper from PSA, do I need to be concerned about headspace, or are they pretty reliable?


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Posts: 2620 | Location: WNY | Registered: April 11, 2009Reply With QuoteReport This Post
fugitive from reality
Picture of SgtGold
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quote:
Originally posted by wreckdiver:
I'm learning more and more about these builds as I go. I got a complete upper from PSA, do I need to be concerned about headspace, or are they pretty reliable?


A manufacturer should check headspace on an assembeled upper if it came with a bolt. They may check assemebeled uppers for generic headspace, but in the end it's up to you.


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Posts: 6555 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
fugitive from reality
Picture of SgtGold
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Op's question is an interesting one. In my experience I've never had an AR that I put together come up with a headspace issue. Other than trying different bolts, the only shop fix I know of it to machine the back of the locking lugs, and that only works on short head space issues. On the subject of gauges, the military uses a gauge with the base of the rim machined to accept the ejector. If you have that done to your guges, you don't have to dissasemble the bolt to check headspace.


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Posts: 6555 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
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I got tired of pulling the ejector so I just machined the same slot the milspec ones have, but I have access to the tools to do that. You might (I haven't tried) be able to do it with a grinder since its not a precision thing. But pulling the ejector is not some voodoo project and really all you need is a punch so I wouldn't let that stop anyone from checking.


“So in war, the way is to avoid what is strong, and strike at what is weak.”
 
Posts: 8450 | Registered: October 14, 2004Reply With QuoteReport This Post
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quote:
A manufacturer should check headspace on an assembeled upper if it came with a bolt.

I would have complete confidence that was true for any top tier mfg. The PSA's of the world, not so sure. If it was me I'd ask them, and then probably double check it myself as well.


“So in war, the way is to avoid what is strong, and strike at what is weak.”
 
Posts: 8450 | Registered: October 14, 2004Reply With QuoteReport This Post
quarter MOA visionary
Picture of smschulz
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While I have the gauges and measure I haven't had any issues with any new builds.
I have bought a matching bolt with barrel on occasion if I can though.
More important for bolt actions, larger caliber rifles and for mostly for custom hand loads.
Always good to check.
YMMV
 
Posts: 17809 | Location: Houston, TX | Registered: June 11, 2006Reply With QuoteReport This Post
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I can't imagine what exactly "more important" means? Any gun with incorrect headspace is a potential issue. And I can't imagine lots of people building their own "bolt actions, larger caliber rifles" and/or where the builder didn't confirm the gun is safe since mostly in those cases you have to chamber the barrel to make it all work. But in any case the intersection of the potential problem and volume is in AR type rifles. EVERY rifle should have its headspace confirmed. Every single one of them. IMO.


“So in war, the way is to avoid what is strong, and strike at what is weak.”
 
Posts: 8450 | Registered: October 14, 2004Reply With QuoteReport This Post
quarter MOA visionary
Picture of smschulz
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quote:
I can't imagine what exactly "more important" means?


It is my primary hand loading effort.
NEVER said incorrect isn't important.
BUT never had ANY issues with the 223 platform.
Also said it is good to check them all.
Eek
 
Posts: 17809 | Location: Houston, TX | Registered: June 11, 2006Reply With QuoteReport This Post
Plowing straight ahead come what may
Picture of Bisleyblackhawk
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We have local AR15 bunch that loans/swaps/make available to club members anything that they need...including the go-nogo gauges...I can’t recall the last time a builder had an issue with the headspace on an AR build...this being said...if possible check the headspace for your peace of mind...just saying Wink


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"we've gotta roll with the punches, learn to play all of our hunches
Making the best of what ever comes our way
Forget that blind ambition and learn to trust your intuition
Plowing straight ahead come what may
And theres a cowboy in the jungle"
Jimmy Buffet
 
Posts: 9936 | Location: Southeast Tennessee...not far above my homestate Georgia | Registered: March 10, 2010Reply With QuoteReport This Post
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Picture of kimberkid
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So with all this talk about AR head space, I've been thinking ... in any other gun I built would ... when I built AK's I always checked them, however I always built from matching parts kits and never had a problem, but I did drill the receivers for the trunnions too.
When I built a couple Mausers into 308 and 22-250 I paid a smith $80 to do the finish reaming and set head space.

Anyway, I haven't found my 223 set anywhere and got a real eye-opener when I went to buy a set on Amazon Prime ... $110 for go, no go & field. To check all my AR's, I need a set of 5.56 too ... even my "factory" guns, most I didn't buy new so I really don't know if they're all original parts or if someone along the way has swapped parts out.

That being said, is a field guage actually sufficient?
I know its better than nothing but ... ?

On one hand ... I don't want to be cheap, but on the other I've never had a problem.

Advice?


If you really want something you'll find a way ...
... if you don't you'll find an excuse.

I'm really not a "kid" anymore ... but I haven't grown up yet either Wink
 
Posts: 5199 | Registered: January 11, 2007Reply With QuoteReport This Post
fugitive from reality
Picture of SgtGold
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You can do a quick and dirty with an empty cartridge and a correctly seated bullet. If you can chamber and extract the bullet without unnecessary force, and the bullet doesn't show signs of hitting the lands, you are probably a 'go' for headspace. Trying this with a live round could result in a slam fire.


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Posts: 6555 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
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Picture of maladat
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I have a friend that experienced the opposite problem.

Building a lefty 6.5 Grendel AR shortly after the introduction of the cartridge, he had to source parts from a bunch of different places, and the rifle he ended up assembling wouldn't fully close the bolt on a round or on any of the headspace gauges. It wasn't just a little off, either. It was off by a lot.

I forget the exact details, but apparently early on for the Grendel, there were basically two different depths they bored the bolt recess out to that hadn't been completely standardized, and he ended up with a barrel headspaced for a deep bolt, but had a shallow bolt. It took a while to figure out exactly where the problem was because he didn't assemble the rifle until a couple of years after getting the parts, and by then everything had been standardized and the issue had pretty much been forgotten by everyone.

Not an issue you should run into with a normal AR, but you never know what you'll come across with an oddball.
 
Posts: 5320 | Location: TX | Registered: January 24, 2011Reply With QuoteReport This Post
Plowing straight ahead come what may
Picture of Bisleyblackhawk
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Brownell’s is your friend Smile


********************************************************

"we've gotta roll with the punches, learn to play all of our hunches
Making the best of what ever comes our way
Forget that blind ambition and learn to trust your intuition
Plowing straight ahead come what may
And theres a cowboy in the jungle"
Jimmy Buffet
 
Posts: 9936 | Location: Southeast Tennessee...not far above my homestate Georgia | Registered: March 10, 2010Reply With QuoteReport This Post
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quote:
That being said, is a field guage actually sufficient?

I would get a nogo gauge rather than the field if I was just getting a single gauge. At least if we are talking new build firearms. Your cartridges will tell you if you have go issue.


“So in war, the way is to avoid what is strong, and strike at what is weak.”
 
Posts: 8450 | Registered: October 14, 2004Reply With QuoteReport This Post
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Picture of Rustpot
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I own a .223 Go, a 5.56 Go, and a field that is the same for both. It's a set with a GI cut (no disassembly required) Brownells Forster gauges selected and prepared by School of the American Rifle.

I'd say you're fine with a field gauge instead of a nogo. Keep in mind not every brand uses the same measurements for their gauges.
 
Posts: 5822 | Location: Romeo, MI | Registered: January 03, 2009Reply With QuoteReport This Post
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Of course your last statement is the key. not everybody uses the same measurements for the same thing. But in any case almost everybody considers the field gauge (especially a 5.56 COLT field gauge) the last acceptable limit before you have to take action to rectify a safety issue. That would not be my first choice for a gauge on a new rifle (the original OP). Sure if it passes that its safe to shoot at least temporarily. I really suggest one get a 5.56 NOGO and be happy at least with respect to this thread.


“So in war, the way is to avoid what is strong, and strike at what is weak.”
 
Posts: 8450 | Registered: October 14, 2004Reply With QuoteReport This Post
fugitive from reality
Picture of SgtGold
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Here's some info on the need for, or lack there of, the extractor\ejector cut on a headspace gauge.

https://mansonreamers.com/2016...on-headspace-gauges/


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Posts: 6555 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
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I bought headspace gauges to KNOW my headspace is good not THINK or ASSUME that it will be fine.


Remember, this is all supposed to be for fun...................
 
Posts: 3836 | Registered: April 06, 2007Reply With QuoteReport This Post
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Picture of Rustpot
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quote:
Originally posted by SgtGold:
Here's some info on the need for, or lack there of, the extractor\ejector cut on a headspace gauge.

https://mansonreamers.com/2016...on-headspace-gauges/


They leave out the part where it's required for mil because not having them wears out your gauges if you don't disassemble the bolt. Gauges are not to be used under spring tension, that makes them into paperweights. You're also cramming a hardened steel gauge under your extractor rim, designed for soft metals- or heaven forbid snapping the extractor over the rim with the gauge in the chamber. And leaving the ejector in place means you need to fight the somewhat heavy spring and force the gauge into the chamber with extra pressure from the rear to seat the gauge as it drags across the wall of the chamber, which is also a terrible idea. Plus you're now extracting your precision gauge and skipping it across the barrel extension lug area as it tries to eject off the face.

None of these conditions are acceptable use for a ground, toleranced, precision gauge. I am baffled that a "precision" company would publish that. Perhaps they expect you to use it only a few times?

If it's a one and done scenario, have at it. I've used mine quite a bit, am considering pursuing armorer work as a side business, and I do not want to be pulling ejectors all the time, so I went with the modified gauges.
 
Posts: 5822 | Location: Romeo, MI | Registered: January 03, 2009Reply With QuoteReport This Post
Freethinker
Picture of sigfreund
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This is something that struck me in that article: “If the cartridge rim will slip under the extractor, the rim of the gauge will also.”

That is of course a big if. The cartridge case rim will “slip” behind the extractor hook of the so-called “controlled feed” bolt, but that extractor design is not used with all rifles. The extractor hooks of all my long guns, Sakos, Tikkas, M1A, and AR-types, all must snap over the case rim as the cartridge is chambered, and that would be necessary when using a headspace gauge if the extractor wasn’t removed.

And as I started this thread, I’ll drift off a bit by raising this point.
I don’t know how many hobbyists there are who assemble their own ARs or switch barrels, but I would guess that it’s significantly more than the number who also have and use headspace gauges (two conditions usually make the probability less than one condition). Perhaps I’m wrong, but if that’s true, and if confirming proper headspace is so important, why don’t we hear of more problems resulting from failure to do that?

I’m reminded of the complaints about bullets being seated too deeply in their cases in factory ammunition. Those reports were especially common during the shortage years when factory QC seemed to slip. Posts about someone’s finding handgun ammunition with bullets seated too deeply were usually accompanied with a touch of hysteria about the possibility of excessive chamber pressures and catastrophic failures. The only thing was that although the complaints were relatively common, what we never heard about was guns’ blowing up as a result.

If failing to confirm proper headspace is a dangerous practice and a significant percentage of AR barrels don’t have proper headspace, then why don’t we hear of the bad consequences? Do they happen and we just don’t hear about them? Does everyone check the headspace of their builds? (I know from personal experience that that’s not true, but perhaps it’s very rare.) Is there some other explanation?




“A man hears what he wants to hear and disregards the rest.”
— Simon & Garfunkel, The Boxer, 1970
 
Posts: 41488 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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