Too little headspace on AR-15 ?

Joseph · Jul 3, 2013

I have a question for the rifle builders here. Back in January I assembled my first AR-15 with parts I had been collecting for about a year. I have not fired it yet and I have a question about headspace.

Using the Forster 5.56 NATO gauges I am having some problems. The chamber wont close on the MIN gauge as I understand it is supposed to. Obviously it wont close on the MAX either, but that is a good thing.
I can chamber live rounds just fine (Federal, American Eagle, PMC) but have not fired it yet.

The rifle was assembled by me using striped LRB upper and lower receivers. I torqued the barrel nut to spec per the JP enterprises full float hanguard instructions.The barrel is a 5.56 chambered black hole weaponry barrel from one of the group buys and the BCG is a WMD Nib.

Should I be concerned about the apparent too little headspace?

sailskidrive · Jul 3, 2013

That's weird. Do you have another gun you can test out the head space gauge in?

K.C.Dean · Jul 3, 2013

Just curious did you remove the extractor? Did you remove the extractor spring and put the extractor back in?

Jerry M · Jul 5, 2013

if the Bolt is not mil spec it can cause head space differences.

Good luck

Jerry

lee2 · Jul 6, 2013

To get the true reading, you need to pull the extractor/ejector off the bolt, and then ride the bolt/carrier closed by hand. Allowing the Bolt to snap/slam closed using the recoil spring is not the way to use the gauges.

smdub · Jul 6, 2013

lee2 said:
To get the true reading, you need to pull the extractor/ejector off the bolt

I see some old timers say this but is doesn't make any sense to me. If you put the gauge in the chamber first, then yes the extractor needs to be removed as it wont ride over the lip (extractor will likely hit the chamber wall first.) But if you hook the gauge under the extractor and hold it straight (the ejection pin may want to tilt it a little) as you gently slide the bolt closed all is good. The extractor doesn't interfere w/ the datum line or bolt face and wont affect the test. I've got about a dozen Manson gauges and they work fine w/ the extractors in place. Now, I'm SURE there are rifle designs that are exceptions but the ones I've tested (AR10/15, SKSs, VZ58, etc) the extractor can't possibly press on the bolt face of the round. Its smooth on the side and just not mechanically possible. It is probably a good idea to press the ejection pin in to verify it will go below the bolt face. A 'long' or stuck one of those can affect the reading. But the engineer in me calls BS on needing to remove the extractor on many (maybe not all) firearms. A TINY bit of carbon on the shoulder, rim (if not rimless), or bolt will cause 100x more problems. The chamber needs to be oil free and cleaned w/ a lint free wipe. Oil/lint easily exceed the tolerances you're looking to test.

jr88 · Jul 6, 2013

If you go to the Brownells site and view the videos for headspacing, they say to remove "ejector". Nothing is said about removing extractor.

Joseph · Jul 8, 2013

Thanks for the replies folks.
I did remove the ejector spring but not the extractor. I will try it again and I will also try a spare BCG I got from JoeBob. I don't have another rifle to test the gauges on though.
What are the ramifications of having less than optimal head space? I understand too much is really bad, but too little? It does chamber rounds without any fuss.
Thanks.

commiezapr · Jul 9, 2013

Too little headspace can also cause the round to rupture, but most of the time the round can't even be chambered.

Too little headspace on AR-15 ?

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