No, chamber fluting (a la HK's chamber fluting) only helps with extraction.  The "extra space" in the flutes is trivial (even when we're talking about a difference of 0.004" in chamber length).  

The blown primer/stuck case scenario is the first hint that something bad can happen.  You could blow out a case.  That leaves a mark, and typically the mark is on expensive parts.  The KB possibility is definitely there, since functionally the tight chamber is no different from a too-hot load.  EVERY "too hot" or "too tight chamber" situation has the possibility of harming the shooter or someone nearby.

I am failing to see where a bolt that is closed and fully locked on a chambered round will create excessive pressure.

Now if the neck becomes constricted or the ogive of the bullet is jammed into the lands then that is a different story. If there is proper neck clearance and the bullet can jump to the rifling then the fact that the bolt is closed on a case with effectively zero clearance from the bolt face to the shoulder datum should not adversely affect pressures. This is in fact describing what happens when loading cases in a bolt gun that have only been neck sized with zero shoulder bump.

I think the difficulty in picturing this comes from picturing where the short chamber will contact the "not short" case.  When you neck size or "zero shoulder bump" size a case, you're still reducing the diameter of the case at the base of the shoulder, even if you're not moving the shoulder back.  And when you do this, you're fitting that case to your specific chamber.  The situation I'm describing is when a standard round is chambered in a short chamber.  Remember, we're talking about the precise location of the shoulder in the chamber.  This is not a "perfect fit" at all.  It's an interference fit, which can keep the case from releasing the bullet appropriately.

In the post I linked to above, the shooter had primers pop with a short chamber.  What else causes primers to pop?

It takes a combination of really short chamber shoulder and really hard chambering (like with an extra power recoil spring) to lead to really dangerous pressure levels, but that's not impossible.

From a more pragmatic point of view, a short chamber over works your brass the way a long chamber does, but instead of a known location on the case to look for these indications, it'll work the web of the case and you'll see loose primer pockets due to the extra stretch of the case web.

Neck sizing doesn't work like that. Neck dies only touch the OD of the neck. No way the RTB force of an AR action is going to reduce case capacity enough to cause a pressure problem. Differences in case volume would be much greater than any chambering force could create

I have Go/No-Go gauges for 5.56 NATO and 300 Blk.  

When I ordered my 300 Blk gauges, they were on back order.

I assembled an upper not having them, and then resized 300 pieces of sized brass because they wouldn't chamber even though they fell into the good range of my case gauge.  Lo and behold, when the gauges arrived, the chamber was short.

Had I checked beforehand, I could have saved myself from having to order another crush washer, and the trouble of disassembling the upper to send the barrel back.


Sixty dollars isn't too much of an investment to guarantee first time quality.  And just think, you'll be the friend with all the "right tools" to build an upper...

I built each one and shot, putting the extra money into quality parts instead of gauges to make sure they're safe.

That's what the factory should be checking, not me.

And I even use Armalite's barrel break in method, though a bit more expedited for an AR vs what I did for my presicion bolt gun.

ETA: Though if it was a barrel/gun of the quality most people on here are building/buying; I wouldn't bother with any break in at all, and I would want to check headspace and generally not trust the weapon till about 1k rounds.

After seeing about a dozen of different bolts pass the test on about a dozen of different barrels, I don't really bother anymore. I've never encountered an out-of-spec bolt and/or barrel extension.

Bolts have a .003” tolerance range.
Unless the manufacturer checked headspace with the bolt that will be used in the weapon their check may not be good with your bolt.

Not arguing, just theorizing.  I have seen strong recoil springs do some major damage to rounds that didn't quite line up properly.  And I'll point out that neck sizing isn't ONLY done with special neck sizing dies - a lot of people adjust standard dies to just resize the neck, but that WILL touch the outside of the shoulder.

The small change in case volume, along with insufficient clearance in the chamber CAN increase chamber pressure.  And remember, I'm not the one that mentioned having popped primers; something made that happen, something related to the poster's incorrectly chambered barrel.  Whatever it was I will not accept a barrel that does not pass a GO gauge test.  There are too many issues that could potentially crop up for me to be comfortable with it.  Besides, if it doesn't pass the GO test, it doesn't meet specs for that caliber.  Who wants to go with an out of spec barrel?

Nobody wants an out of spec barrel.

To be clear about the neck sizing thing, if a FL die is being used as an impromptu neck die then that process is being done improperly and will actually lead to the shoulder being pushed forward instead of being left untouched.

All that being said, neck sizing has no place in a gas gun reloading operation.

If the "popped" primer rifle had a chamber that was not to spec in regard to headspace then it could be assumed that the chamber was cut with a reamer that was worn beyond tolerance. If that is the case then the chamber could have had an undersized neck, and that can surely lead to pressure problems. This is much more likely to be the culprit than a chamber that is .001" short. The GO gage provides a reference to indicate that SAAMI ammunition will chamber correctly in that rifle. The NO-GO gage indicates that if SAMMI spec ammo is used in that rifle an excessive headspace condition will exist and the subsequent dangers that go along with it.

If the other guy's chamber was short because of a worn reamer, you have a great point, and this is probably why most GO failures will occur.  But with the large number of barrel makers out there today, it's not the only reason a barrel will fail a GO gage.

I had a 300 Blackout barrel fail the GO gauge by a LOT; the bolt had about 1/4 of the lug still hitting the barrel extension lugs.  That's not a "worn reamer" problem, it is a "they didn't do it right" problem.  In this case, there was no telling how much variation there was from one barrel to the next - my vendor gave me a full refund and told me he shipped the whole batch he had bought back to the maker because he'd had so many complaints of bad chambering.  

If a barrel fails a GO gage, I'm not going to try to troubleshoot it, I'm going to return it.  I think this is the only way to ensure a safe barrel and bolt combination, especially now that there are so many different barrel makers in the game, with anything from tons of experience to almost none at all.

As for NO GO gages, if I'm installing a NEW barrel and it fails a NO GO test, that says that the new barrel is nearly at that excessive headspace point - and that's "out of spec" as well.

I see all these posts in this thread about failed head spacing but no one is saying what brand of barrels and bolts they were using. If you use quality parts, head space is a non issue. I have built probably 10 uppers with no issues. I don't use cheap parts though. The market is flooded with so many cheap parts that if i was buying cheap parts then i would probably check the head space.

Always check headspace.


If you have ever worked in manufacturing you would know there are going to be MAX and MIN Products going out the door, not on purpose but it does happen.




Name brand crap even has this happen.

Colt Bolt, Bushmaster Bolt, and PSA bolt with an AAC Barrel.

It's not just cheap parts.  Shit happens, QC/QA gets lazy, production guys get in a hurry, things are good prior to surface treatment and don't get checked afterwards.  

Trust but Verify.


You're free to do whatever you want, but I will check my work and know that it's right.

Where the fuck can a man just order a set of three gages(go, no-go, and field gage) in 5.56, NOT .223??? My goddamn search is turning up everything except what the fuck I want/need.........

Would a set(all three) from Fulton be worth a shit? I'm about ready to say fuck it and just stick to what I've been doing(not checking headspace on my builds).

Forster

Check Brownells. link I ended up buying Manson gauges. If I were to do it again, I would call or email Manson directly and get their "down and dirty" gauges because if I understand correctly, you don't have to disassemble your bolt to use them. That ejector roll pin was a real bitch to get out.  I ended up having to buy a bolt disassembly tool. I also purchased a 5 pack of ejector roll pins when I bought the disassembly tool to be on the safe side and ended up needing to use one of them because the one I took out split when I tried to put it back in and yes, I was using the proper roll pin punch.

I bought my Forster gauges (minimum/maximum) off ebay, it was less expensive than ordering directly from Forster.

Brownells sells them also.  I forget the brand that has the cut-out for the ejector, but that might be handy.  

A .223 gauge and a 5.56 gauge that is marked with the same dimension, is the same, if I'm not mistaken.

Thanks guys!!