I have aquired a set of 223 headspace gauges marked GO/NO GO/FIELD.  Now how do I use them to make sure my AR is headspaced properly?

The if your bolt closes on the "GO" guage, but not on the "NO GO" guage, the head space is correct. So the chamber is the correct size.

If your bolt closes on the "NO GO" guage, but not on the "FIELD" guage, the headspace is considered slightly excessive. This could mean a dirty chamber or the chamber is on the large size. If you have access to box of bolts, you might be able to find one this on the large size, to correct he headspace. Anyway the manual claims it is still "safe to shoot mil spec ammo"??

If your bolt closes on the "FIELD" guage, you are in trouble. This indicates the the headspace is dangeously too large. Do not attempt to fire any rounds through this barrel!!! The rifle can suffer a blowout(casehead seperation) with catastrophic results!!!!!

Good Luck,
Stuart

Ok, I must be missing something here or am doing something wrong.  I had several friends bring over there AR's to see what I can come up with.  I have tested 4 AR's tonight and here is what I have come up with.
I inserted the gauge into the chamber and allowed the bolt to come forward and close.  Of the 4 AR's 3 closed on all three gauges.  These were a PreBan Colt, Preban Oly and a Postban Bushy.  The last one closed on the GO.  This was a factory RRA upper.  All firearms have less then 600 rounds through them.  

So from what I have read above 3 of these rifles are going to blow up?  

Help me out somone....

Here MIGHT be your problem.  There are "223" gauges, and then there are "M16/AR15" gauges.  This boils down to the fact most AR-15's are 5.56 mm spec chambers, which is slightly larger than a .223 chamber.

I recommend purchasing a set of gauges from BUSHMASTER.

[url]http://www.bushmaster.com/shopping/gunsmith/hg0223g.asp[/url]

I use the Bushmaster gauges on my AR's (all bushmasters).  These work great.  It closes on the GO, and fail to close on the NOGO.

My bad, these are .223 gauges and all but one of these rifles are chambered in 5.56.

That might be the problem then.

Hi guy,

I don't understand how you used the gauges.

Did you take the extractor and ejector off/out of your bolt?

A lower receiver's buffer tube and spring are not involved in the test.......just a very soft touch with your hand.

Dave S

Dave,

I guess I dont understand your question.  

Tell me then how do you properly check headspace.  Start at the very beginning and go step by step.

That's your problem.

Remove the extractor/ejector before.

The upper doesn't need to be attached to the lower at all.  Just drop the guages into the chamber, and push the bolt closed.

But if my chambers are 5.56 a .223 gauge won't work will it?  I wouldn't think so, I would imagine that I would have to get a set of 5.56 gauges.

You'll be fine with a .223 gauge in a 5.56.

Ok, just to muddy the waters...

First off, all have given excellent advice to remove the extractor and ejector.

But, I am somewhat lazy.  I just remove the extractor, which is much more easy to remove than the ejector.  I do not see how the ejector will harm anything by remaining in the bolt.

Second bit of advice.  Use a 10 pound excersice dumbell to place on the end of the carrier to test the GO gauge.  This technical poundage is 8 pounds, but the I have no 8 pound dumbells.  The bolt should close on the GO gauge with 10 pounds or less of pressure.  To test the NOGO, I place a 50 pound dumbell on the carrier.  As long as the bolt stays unlocked behind the 50 pound dumbell while using the NOGO, I am happy.

Ok Guys I have remove the extractors and this is what I came up with.  Using .223 headspace gauges Go/No Go/Field.

Colt-closed on all gauges
OLY-closed on Go and No Go
RRA-closed on all gauges
Bushy-closed on Go and No Go

So WTH are these guns going to blow up if we shoot them?  All guns have less then 600 rounds through them.

Any thoughts?  Am I putting to much thought into this?

I've always wondered about checking head-space. Contact mstn or someone else who actually build ar's from parts

[url]http://www.ar15.com/forums/topic.html?b=3&f=7&t=142139[/url]

the problem is you're using .223 gauges, on 5.56 cut chambers....and  despite what bigD said, there is a difference in the size of these gauges, you can't use a .223 gauge in a 5.56 chamber. if you get the  USGI 5.56 gauges, you don't need to take out the extractor or the ejector.

the only thing I would worry about, is rifles that aren't assembled by the manufaturer...factory assembled weapons are check for headspacing before they leave ......it's the unscrupolous dealers, and folks that will sell a "parts gun" that will put in a used bolt in a upper and not check to insure it's headspaced

I recently purchased an A2 upper with complete bolt carrier assembly. I do not know the history behind this upper.  Do I need all three headspace gauges or can I get away with just one or two headspace gauges? Like the "Go" or "No-Go"  [8D]

Get the guages from bushmaster.  I compared the ones I got from Bushmaster to the ones I got from Forrester and there was significant differences.  At $17 each they are worth it.

if the complete upper didn't come from say RRA. or BUSHMASTER etc... I would be very wary that it might not be correct. 99 percent of the time a new upper, with a new bolt will probably headspace correctly.....but it's that 1 percent that I'd be concerned about. you can buy the gauges...but it just dawned on, why do that?

ordering the gauges, pay for them and shipping, and then wait.....take the upper to a competent gunsmith and have him check it for you, probably will take 10 minutes or less, if he's not busy at the time,  it should cost but a few bucks,  a competent smith will have those gauges already....you don't really  need to buy gauges if you are just going to check, for your own piece of mind........now  I can see buying them if your going to be building a AR upper from scratch.

in any event, that's what I would do.

First, send those four rifles to me so that they can be properly disposed of.  No, just joking.  Seriously, read on:

[b]So from what I have read above 3 of these rifles are going to blow up?[/b]

No, they are all safe.

[b]My bad, these are .223 gauges and all but one of these rifles are chambered in 5.56.

That might be the problem then.[/b]

No, that is not the problem, either.

[b]Here MIGHT be your problem. There are "223" gauges, and then there are "M16/AR15" gauges. This boils down to the fact most AR-15's are 5.56 mm spec chambers, which is slightly larger than a .223 chamber.[/b]

BINGO!!! We almost have a winner!!!  The M16/AR15 has a larger chamber that enables  better feeding and extraction with its self loading feature.  You cannot check headspace on an M16/AR15 with .223 gauges.  Well, you can, but you get erronious results.  

It does not matter if it is a .223 chamber or 5.56 chamber, .223 gauges do not work.  Both chambers in a M16/AR15 are larger than what is found in a .223 bolt gun, it is the leade, or freebore, that is different.

[b]Ok Guys I have remove the extractors and this is what I came up with. Using .223 headspace gauges Go/No Go/Field.

Colt-closed on all gauges
OLY-closed on Go and No Go
RRA-closed on all gauges
Bushy-closed on Go and No Go

So WTH are these guns going to blow up if we shoot them? All guns have less then 600 rounds through them.[/b]

All of these rifles are safe to shoot.  The best indication of unsafe headspace is from examining the brass, look for shiny rings around the circumference just above the web of the case.  That is where brass will stretch from excessive headspace.

Sell your .223 guages to someone, if you can find them, that shoots a .223 bolt action varmint or target rig.  Your gauges are useless, no, worse, for checking AR15's.

Forget all this fiasco, and just go shooting.

I'd agree with that!

If you want the proper gauge order the US Military FIELD GAUGE from Fulton Armory.  Comes in a nice foil wrapper and has the calibration card.

This should be the only gauge you will need - The other nice thing about it (other than its what you're 5.56 chambers were meant to use) is you don't need to dissassemble your bolt.  The Military gauge works with everything in place.

OK, after following this discussion on headspace, I decided to check mine. I ordered a field guage from Fulton Armory. It arrived today. Just how is it used? Do I just drop it in the chamber and close the bolt? Should the bolt close on it or should it not? Help please.
Thanks.

if you got the USGI one, then it's a simple matter of taking the upper off, or break it down like a shotgun, put the gauge in the chamber, and then  by hand push the bolt group up to it, then with just thumb pressure try to see if the bolt closes....... the bolt should not close.

don't slam the bolt group into the gauge.