I've read through the topic tacked at the top of the page. I've looked into some gauges but there are a ton of different brands with different options. .223, 5.56 and so on.

This one would fit the bill or would I need something else?

Thanks
Paul

If you insist on getting a headspace guage is it a .223 or 5.56 x 45 barrel? If it is a new barrel you'll want a no go for the appropriate chambering.......but honestly...I have them but only use them when making a barrel from a blank where I am fitting the extension and then chambering it myself. If you have a new bolt and a new barrel.....you are good to go.

It's a BCM bcg and a PSA barrel made by FN. I didn't think that I needed to check it....my gunsmith told me you should always check though so it has me rethinking

It's a 5.56 barrel btw

That gage by itself only tells if the weapon is safe/unsafe to fire with 5.56mm ammo.
It does not tell how close to unsafe a weapon may be.
Never the less a bunch of people here find that sufficient.
I manage my personal weapons to keep them within the SAAMI (223REM) Field limit which is about .004” shorter.

Both are GtG.  Check if if you like but many here would not bother.  I would not worry about it.  

It is up to you, but if it is bad what are you going to do about it?  Send both parts back?  Which is out of spec, both? It could be tolerance stacking and both are within spec then you really can't send anything back.

Quoted:




I own a lot of AR-specific tools and wrenches, but I've never found the need for a head space gauge. As long as both parts are new you will be fine.



Having said that; I wouldn't attempt to install a BCG with 10,000 rounds of use into a new barrel assembly and expect the head space to be correct.
 

As I said.....I headspace with go and no-go guages when I make a barrel from blank, but not on a kit build........I do however inspect the fired cases from a new build for signs of excessive headspace......even if it is excessive.......it isn't gonna kaboom on you.......I had a surplus GI barrel a few years back......chopped it and built a 7.5 pistol, took it out and test fired it....fired two rounds and "CLICK"......cycled the charging handle....same thing...."CLICK" took it in on the bench and checked for a broken firing pin......then I looked at the fired brass and a light went off.........it had fire formed to the chamber........LOL...the headspace was sooooooooooooooooooooo escessive the firing pin was pushing the round up into the chamber and failing to fire......appearently the barrel had seen a ton of full auto fire......

while it is an interesting story.......don't take my word...pick up a copy of Hatcher's Notebook and in the back of it is the detailed notes of a study done by then Major Hatcher back in the 1920's at Springfield Armory with 1903 rifles M2 30-06 ball ammo and intentionally reaming the headspace to the extreme and then test firing the rifles trying to make them fail. It is truly an amazing study and well worth the read for anyone interested in building and shooting guns. In fact I recommend owning a copy for anyone who is more than a casual shooter. It is one of the seminal references for gunsmiths.

If you have a 5.56 chamber, then that is your gauge.
That gauge can also be described as the Colt II Field Gauge and is the current military standard Field Gauge.
5.56 is not a SAAMI (civilian) cartridge so it's best to ignore SAAMI gauges when dealing with 5.56.

Here's a quote from Bravo Company, one of the most respected AR manufacturers in the industry...

....A little knowledge is dangerous, but if you must mess around with a headspace gauges get a FIELD gauge.
That is the only one you will need.  That is the only one you will need.
Not just any field gauge, get the NATO one that Colt recommends........ (.1.4736”).......(Brownells #319-418-033).
You are not building barrels, you are not fitting bolts. You are in “the field”, and that is your gauge.
Double check the measurements on your gauge.
I have seen many gauges with text and not marked with a numeric measurement and even mis-marked dimensions.
Get rid of them. Just keep the Colt FIELD Gauge

Despite all of the "new parts will be fine advice" on this site, I just put four uppers together and two of the barrels failed to chamber on the "GO" gage.  I contacted the company and they said it was unacceptable and they would send me replacement barrels.  

As far as I am concerned, if you have the time and ability to build a rifle from parts, there is no reason you can't or shouldn't take the time to check headspace.

Just curious ...what procedure did you use in checking the barrels?....and who made 'em....LOL....that is a VERY high almost stastically impossible number of failures in that small a sample. Would the short chambers lock up on a round or did you not check after the go guage failure. Not trying to be snippy....genuinely intersted in your experience on this matter.

+1
As an AR builder I may not normally be ‘fitting’ bolts, but I certainly check the fit because manufacturers make mistakes.
This highlights one of my problems with the Colt field gage as ‘the only gage a person building weapons needs’.

I stuck my thumb in my ass and jiggled it.  What procedure do you think I used?  They are Surplus Ammo & Arms barrels.  I did not try a round and I am not going to.  The gages are there for a reason, and it is to make sure the chamber is safe to use, whether a round fits or not.  SA&A said they would replace them no questions asked.  I am just waiting on word on the details.

But for the record:
I cleaned the barrels and chamber
Removed the ejectors and extractors
Tried four different BCGs
I jiggled the BCGs a tiny bit, then progressively harder to make sure they didn't need the tiniest bit of help
You could see that the bolt fails to rotate almost as much as the "NO-GO" gage (the actual NO-GO gage, not just the field gage) does, so these things are pretty far out.

Also, this is pretty atrocious advice for someone that is new and trying to do things correctly.  The "Colt" gage does nothing more than take away some of the engineering safety factor that is calculated into everything by most manufacturers.  It is most likely only there as a means to extend the acceptable wear and therefore the usable life of a military firearm.  From what I have gathered, the military can use that larger gage because they evolved to using longer and heavier bullets and those can change the dynamics of what is happening during firing.  If you are using more common 223 ammo in your rifle, especially if it happens to be of a smaller gain, and higher powered ammo, that longer chamber could cause the case to stretch excessively and rupture.

Here is a quote I received from Fulton Armory when I asked them why they sent me 223 gages, when their website states 223/5.56 gages.
" We believe that EVERYONE should use the commercial .223 headspace dimensions because it is almost certain they will use commercial .223/5.56 ammunition. The massive headspace allowed for by US & NATO spec’s can and does cause commercial ammo to fail."

As far as I am concerned, the only time you should be using a COLT field gage is if you are a military armorer, or if you are willing to push the envelope with your AR that is chambered in 5.56.  Keep in mind, that field gage is not telling you what a new 223 or 5.56 barrel should be sitting at.  It is giving you the absolute, or damn close to it, limit at which you can still safely fire that rifle.

In case people don't know.  Fulton Armory specializes in building match rifles, and are also heavily involved in shooting matches.  They have been doing so for much longer than BCM has been around.

+1 on Fulton Armory.
I have dealt with them for so long I can’t remember when I started.

The second part of the answer was all I asked for...and politely....I used to check every barrel years ago but as I never found a new one out of spec...I quit.....and as 99% of the barrels I use now I make from a blank I make damn sure the headspace is set correctly......I was simply trying to establish exactly what was happening...if you are as experienced as you indicate you know full well that a lot of people wouldn't know to remove the extractor and ejector prior to checking headspace.....As a result of the info coming out I probably will start checking....if the panic buying rush has caused a slip in QC in the rush to ship product....nice thing to know,,,,,,BTW...hope you washed that thumb.......

I know what you were getting at.  But had I not removed the ejectors at the very least, you would have seen me post that all four failed headspace, instead of two of the four, no?

I deal with the public every day in the wonderful world of gunsmithing and engine rebuilding ....been doing it for over 25 years.....and I still get the hell shocked out of me on a weekly basis by people.......It is now ingrained in me to as extremely detailed questions...........and keep askin 'em.....till I find out exactly what happened.....I could bore ya for hours.....but I won't.....

seriously....any Idea who actually made the barrels? Unfortunately I don't know who makes 'em for SA & A

I have no idea who makes them.  I just know they are sending me four new barrels, new crush washers, and new gas tube roll pins.  But the other two that did pass are a different story.

I've read that wacko statement from Fulton and I say wacko because they (Fulton) were one of two sources for the genuine USGI Colt II Field Gauge.
Maybe there was some kind of power struggle at Fulton, I don't know. Actually I don't care.
The Colt II gauge (1.4736") has been keeping hundreds of thousands of safe M16's and M4's in the hands of our armed forces.
That would be more than good enough for me, as I'm not a barrel builder.

Saying "GO" or NO-GO" when discussing .223 or 5.56 headspace gauges means absolutely nothing unless you provide the actual dimension of the gauge. There are too many different gauges in these calibers. They have to be described by their actual dimension.
There is a Forster SAAMI "NO-GO" gauge, for example, that would fail a new chamber.




So in summary, the good folks that allow us to have this friendly chat, have their M16s/M4s checked with a Colt II Field Gauge (1.4736").
Powerful stuff right there, wouldn't you say ?


(better not look at the M249 headspace, you'd sh!t yourself)

Remember.....it is a field guage........if you are checking a NEW unfired barrel...use the guage it was made with ....I have reamers and guages for 5.56 x 45 and .223 and use them as required by the barrel I'm making......and in the future will use them with the barrel I'm checking......as I intend to start back.....but if anyone hasn't.....READ the headspace tests in Hatchers notebook.......I would be MORE concerned about a short chamber than I'd ever be about excessive headspace.......I have fired 5.56 rounds in a barrle that was sooooooooooooooooooooo long chambered form erosion that the rounds wouldn't always fire......yes we were screwing around with a junk pistol build......but when it fired it held up well.......but I have also seen a kaboom caused by a case head seperation and repeated application of the forward assist till it fired......it was at the other end of the line and I was trying to get to the shooter and stop it.

Does this mean the Colt gauge is GTG? It should basically tell you if it safe to fire....not necessarily if the headspace is good?

Another statement which means NOTHING.   I am willing to bet a whole lot of statistics, as well as engineering went into creating that gage.  I am willing to bet that almost none of those rifles ever fail with that gage because there are other factors which put them out of service well before they come close to that measurement.

And it still doesn't change the fact that a new barrel should close on a GO gage, and it shouldn't close on a NO GO gage.  If you are accepting anything close to a COLT field gage out of a new barrel, you are short changing yourself a hell of a lot of shooting before it does reach that excessive limit.

It is good to go for a military spec chamber shooting military spec ammo.

Exactly.....if you are checking a new 5.56 barrel...use a set of go , no-go for 5.56.........same for .223.......

Use whatever gauge floats your boat, GO, NO-GO (undisclosed dimensions, etc).
If you feel so strongly about this, maybe you should write a letter to your congressman.

I don't have to write my congressman to realize what you are advocating is stupid.  You are saying the same thing as, the standard worn gage for tires is 2/32, but one tire manufacturer says 1/32 is okay, while all manufacturers build new tires with 28/32 of tread, but it is okay to accept tires from a manufacturer that builds them with 14/32 of tread because they give you 1/32 more of wear to play with over the ones that say 2/32.

You are advocating accepting a lower standard (more worn) just because that is the extreme limit for military rifles shooting military ammo.  Your precious 1.4736 gage reading is not something you should be shooting for with a new build.

It's past your bedtime, ye olde incorrigible one.
Go to bed.

Military weapons are used with new mil-spec ammo.
Military weapons are inspected on a regular basis by a trained armorer.
Put a reload in a chamber that is near the Colt max headspace, especially one that has been previously fired in a chamber with a lot of headspace and the shooter is asking for a case head separation.
I would also point out that while recalls on new factory ammo are not common they are not unheard of either.
It is obvious you do not understand the issues here which make it near impossible to pick between radically different viewpoints.
Compounding the issue is the fact that it is rare to find a problem, but it does happen.
If you plan to shoot 223REM or reloads I suggest you go to the SAAMI website and read what they have to say.