I am getting ready to start my first build and was just wanting to know if I need to spend the money on them. If so, is there any brand(Clymer, Forster, ?) that seems to be the "one" to get? TIA

If you can search, or if you just hang around, you'll find out that this is a controversial area.

Because of the overall decent quality of parts now days, it is likely that things will fit together fine.  Lots of guys just build and shoot.

Generally, the longer someone is  around, or the more rifles built or the more anal someone is, the more likely to use go and no go gauges.  Forster, Clymer and Manson are all good.  I have and use Forster, but if were buying again it would be Manson.
I routinely check headspace, just another quality check.

I use both brands and always check every build. That's just me. If you are using high quality parts you should be fine but I do not take chances and check everyone.

I use a Field gauge anytime I assemble an upper with a new bcg.  If you only have one gauge a field gauge is what you need.  (If your bolt closes on a field gauge your headspace is too long/unsafe)

Just finished my build yesterday using Go No Go.  Took only a few moments to check but that piece of mind goes a long when I go to  pull that trigger for the first time.  Hell it's cheap insurance at around $70 for the set.

Every build, Every time.

I have go and no go gauges in 5.45x39, 5.56x45, 7.62x39 and 7.62x51 which is basically every caliber I build in. Sure I spent some money, but a face as handsome as mine deserves all the protection I can give it. lol

PS If I could have only one gauge it would be a no-go, not a field as suggested above. A field gauge only tells you that you can fire it if your life depends on it, not whether or not it is within proper spec.

I built my first just using a regular old wrench to torque every thing down.  The torque range is so broad its pretty difficult to screw up.  I still was unsure of myself and took it to a local smith for him to check and it was fine.

Barrel nut torque or lack there of has no bearing on the headspace. That is strictly the relationship between the bolt and the barrel extension/chamber

i dont use one

I use GO/NO GO gauges whenever I build an upper.  Having them in 300 Blackout saved me a lot of hassle when my new barrel turned out to be incorrectly chambered - it would not pass a GO gauge, meaning that the chamber was too short.  I got the barrel replaced with a minimum of fuss because I could prove it was faulty.

Question for you guys that use em, if they are a no go, what do you do?

as maxxx said
Every build, Every time.

just ordered Manson "down and Dirty" .223 gage set. The advantage is that they don't have a rim requiring disassembly of the bolt. According to Manson the .223 will work for the 5.56 .

I didn't at first.  Several builds with no issues.

Then, my last (and favorite carbine build) had issues.  Failure to chamber, blown out primers, etc.  So I bought some head space ga. and checked.  Very tight.  Very, compared to my previous builds.  I had a 20" HBAR clone with a somewhat (compared to my other builds) fit and swapped the bolts and the carbine issues went away.

Even parts from the same vendor will not all be the same exact size.  Close?  Most likely, but not exactly the same.  Get enough parts (or even one, if off enough) that are a little off, and you could have problems.

To pass, a new barrel and bolt combination must close on a GO gauge, and must NOT close on a NO GO gauge.  If it doesn't close on a GO gauge, the chamber is not deep enough (for that bolt).  If it closes on a NO GO gauge, the chamber - while not necessarily "unsafe" - is as deep enough to be considered "worn out."  You surely do not want that with a new barrel.

If the new barrel doesn't pass either test, return it.  I test new barrels before I install them in an upper "just in case."  All you have to do is see if the bolt goes into the barrel extension AND turns to lock.  You should never need to put any pressure on the bare bolt (with the extractor and ejector removed, of course) to close on a GO gauge, and the bolt should not go in far enough to turn on a NO GO gauge.

Go and No-go always no matter who else says they checked headspace on the barrel.
Field gages are for used weapons that were properly checked when new.
Bolts have tolerances and usually swapping bolts on a failed Go gage will get a pass.
I would reject a new barrel that fails the No-go gage no matter what bolt I used to test.
If you think about it failing a 5.56 NATO No-go gage means more than half of the total available headspace is gone before a person fires the first round.

these here? http://www.brownells.com/gunsmith-tools-supplies/measuring-tools/headspace-gauges/rimless-rifle-shotgun-cartridge-headspace-gauges-prod25179.aspx     & for anyone wanting the website. http://www.mansonreamers.com/  



 

I've seen brand new stuff that will close on a "no-go" With that being said........"field reject" is required.......Most people that only have one gauge will have a "field reject" which means.........UNSAFE TO SHOOT

Seeming how the barrel can only go in one way headspacing isn't really necessary.If you're building an AK then I would say yeah get some but AR's are pretty to hard to screw up, unless you over torque the barrel and shear off the indexing pin.Hope this helps

Me neither.  I ALSO like to live dangerously....

Why is it not really neccessary to check headspace because the barrel only goes in one way?

I used the Clymer set. They aren't the cheapest tool and many say you can go without it. While I don't exactly have money to throw away I can make more money. If there is something wrong with the build matching up and because I didn't take the time/money to check it and it goes boom It'll ruin your day. Be smart and be safe. If you can't get the gauges check with the hometown section and see if you can meet up with someone local that has them and borrow them. It only takes a couple minutes. Good Luck.

here's to the guy that says you don't need to check headspace on new builds--upper minus bcg came from PSA and the bcg and chg hld came from Surplus Ammo. Got my gages from Manson today and  started assembling the rifle. Got as far as checking the headspace and low and behold the bolt would not lock on the go gage. Fortunately I had a few extra new GI bolts and  things clicked. If I hadn't checked and just slapped everything together and test fired it things could have gone badly. It would have possibly fired from an open bolt. Use your imagination on the results.    Safety and common sense are the best tools in the box   TG

Here's a great description of what the different gauges measure, from Forster's site:

I check every upper I have, even if it's supposed to be a factory tested upper. The gauges are cheap compared to replacing a blown up gun or fixing bodily damage. Plus I like to tinker with guns so it's a win/win.

I only bought and use a no-go gauge.  I use a live round for the 'go'.  No lock on no-go and a lock on the round and GTG.

Live rounds, snap caps, dummy rounds, or whatever are no substitute for Go gages.
Live rounds are made to an entirely different tolerance range.
The SAAMI cartridge spec allows the ammo to be longer than factory ammo typically is.

Same here I only have the Manson no-go gauge and check my go with all my live ammo.......Manson has all three gauges for I think $60 last time I looked.

Again, live rounds are no substitute for a GO gauge.  SAAMI specs for cartridges are completely different from specs for chambers.  There is a substantial, specific amount of clearance built into that difference.  See the quote above from Forster: the SAAMI minimum chamber will accept a SAAMI maximum cartridge.  Any reputable ammunition maker won't ship ammo that is at maximum dimensions, they'll go for something between min and max, for better compatibility.  So if you use a live round (and I shudder to think about how some people might do this headspace check using a live round!), a non-spec, below minimum chamber might take that round...but if you fire a "warmish" round in that chamber, you could wind up with a serious overpressure issue.

Looks like I will be purchasing a set of go/no-go gauges in the near future. Thanks for everyone's input. I really like the idea of not having to take the bolt apart to use them but the idea that .223 gauges will work for a 5.56 barrel seems strange to me. I know Forsters site says to use their 5.56 in 5.56 barrels.

reccommend you get them directly from Manson Reamers. His website does not accept orders so call them at 810-953-0732. The ones on the Brownell's website are shown with rims and a slot. Manson "DOWN AND DIRTY" are the way to go.

On my recent pistol build, I had the headspace checked at a local shop.  The bolt was closing on the field gauge.  Turned out to be the bolt, not the barrel.  The lugs on the bolt were measuring .006" shorter than the lugs on my fairly new Colt bolt.  The lug face to the bolt face was the same, so the discrepancy was on the rear of the bolt lugs, which allowed the headspace to be excessive.  I returned the bcg to the store where I bought it, and upgraded to a PSA bcg for an extra $25, after measuring a few more of the other brand bolts.  They all measured the same, too short to give a good gauge reading.

The difference in 223 REM and US mil-spec chambers where headspace is concerned is in the Go, No-go, and Field specs.
A 223 REM match gage set also covers the US 5.56mm mil-spec range.

I always measure lug length and face depth on bolts.
It is interesting you found one that was so far out of spec.
What do you mean the other bolts were too short to give a good reading?

IIRC, my Colt bolt measured..179" on the lugs, and the others, all new, measured .173", which would all result in a fail on the field gauge.  My PSA bolt measured .178" new.

the only concideration is the distance from the bolt face to the REAR surface of the lug

I was informed by a local gunsmith that you cant change the head space on an AR barrel. Its done by mfg. It is worth while to check, but there is nothing that can be done about it (So I am told).

Yes, there is something you can do about it.  Return the barrel.  If multiple bolts won't properly headspace with the barrel, there's probably a problem.  If the FIELD or NO GO gauge fails, then measuring the bolt face depth and lug length is useful to ensure that your bolt(s) is/are within spec.  Then provide that data to the vendor you got the barrel from for refund or replacement.  I did this with my first 300 Blackout barrel...

Headspace certainly can be corrected by someone with the skills and equipment.
Just because it can be done does not mean it is worth it or desirable to do.
However as GHPorter already pointed out a person simply returns the barrel or upper assembly as the case may be.

Yes, i perhaps should have stated you can return it, but its not worth it to be corrected.

I bought the Manson Go and NO/GO gauges from Brownells and the description says "rimless" but they sure seem to have a rim with a slot cut in it. I am not sure if I need to disassemble the bolt or not or can I just take the bolt out of the carrier and check? The barrel is not installed on an upper yet. I have two different BCGs, Wilson Combat and Diamondback, both semi-auto and brand new.

Double tap

Good name brand barrel/bolt I wouldn't worry about it being unsafe. If you're buying questionable stuff, I'd buy it for peace of mind.

I built a 24" bull barrel vARmint rifle.  No issues.

Then I built 3 A2 flat top clones.  No issues.

Then I a couple of 16" M4 clones.  No issues.

Then, for my last AR build (yeah, right) I built the 16" carbine with all my really wanted pieces on it.  Guess what, primers blown out of the cases, failures to chamber, having to tear the gun down (pull the stock and buffer tube and pounding the bolt/carrier out.  It sucked.  I bought some go, no go and field reject ga. for it.  Bolt would close, barely and I mean just barely, on the go ga.  I checked my other ARs and found one that was "loose" on the go ga. and swapped bolts between it and my carbine build and everything has been sweet since - but my chrome bolt is in one of the A2 flat tops and a parkerized bolt is in my carbine build.  

If you build enough, you may run into trouble sooner or later.

I went ahead and bought headspace ga. for .308 and 30.06 to check my M1's and M1A's.  No issues with them.

Just for FYI  I just called my local gunsmith and he said he would torque the barrel to spec, and check headspace while I waited for $35.  That's half the price of a gauge set. Now if you are going to build frequently yeah buy the gauges.

I bought one last year after posting this same question.
I have built three or four since then.
I still have not used the HS gauge.  

I just finished my second build. Still haven't used go/no go gauges. I did the same thing this build I did with the last build. Put the gauges in the shopping cart with my online order of parts and then decided I could use the money on gauges for more parts.

Assuming your bolt won't close on a field gauge but you don't have a GO gauge to test a new build, what's the worst that can happen if the chamber is too tight?  My understanding is that the firing pin can't protrude past the bolt face unless the bolt is locked back, so isn't it impossible for the gun to fire out of battery due to a tight chamber and/or over-sized out of spec ammo?

I don't think you get it.  The minimum chamber (GO gauge dimension) is sized to accept the MAX cartridge dimension, so you [i]should be able to close the bolt on just about any cartridge.  The problem is that a chamber that's too tight will cause high pressures.  Read this post above.  Read it carefully.  You'll get the same sorts of indications that too-hot ammo gives, including blown primers and stuck bolts.

Your description of the firing pin protruding is worded oddly.  Yes, the firing pin should not protrude enough to fire a round unless the bolt is locked, but as I said, a tight chamber won't keep that from happening with a lot of ammunition.  You don't need to worry about out of battery; you need to worry about IN battery but with the chamber too small to allow the case to properly expand, which gives you blown primers, etc.

Here is SAAMI's specification for .223 Remington chambers and cartridges.  Note that it's titled "Maximum Cartridge/Minimum Chamber."  Now note the dimensions in the chamber drawing highlighted with the circled "X" - these are the maximum and minimum headspace values.  The standard .223/5.56 GO gauge is ground for a headspace dimension of 1.4636", which is the minimum headspace dimension in the SAAMI spec, while the NO GO gauge is 1.4696".  The Colt Field gauge is ground to 1.4736", the maximum allowable SAAMI chamber headspace dimension.  (I use the Forster GO and Colt Field gauges.)  

Now look at the cartridge part of the diagram.  The maximum cartridge headspace dimension is 1.4666" (-0.0070) - but manufacturers tend to go short on this for "maximum interchangeability," so you're more likely to see cartridges no longer than 1.4596".  That's lots shorter than the minimum chamber, right?  But that difference is intentional and important.  

Now let's say that you get a barrel that, with the bolt you're using, has a headspace dimension of 1.46000".  That has just enough room for that short-ish maximum cartridge to get in and let the bolt close.  But now, instead of 0.0040" of room to expand, you only have 0.0004" (4/10,000" instead of 4/1,000").  Where does the pressure that would have expanded the case in the minimum headspace chamber going to go?  It'll start by blowing your primer...

Thanks for the explanation.  If the barrel I am using has light chamber fluting, would that help reduce the danger of a tight headspace condition?  Assuming I only used a field gauge to check a new rifle build, is a blown primer and/or stuck case just about the worst I could expect if from tight headspace, or would I also be risking a KB?  I understand that too much headspace is dangerous, and that too little can cause malfunctions that are difficult to clear, but can too little also cause a catastrophic failure that is dangerous to the user?

Short chambers can cause malfunctions, no big deal at the range, but in a HD situation may have unintended consequences.
Good bolts can vary up to .003”.
In my experience it is not unusual to find a barrel/bolt combination that will fail the Go gage.
Depending on just how far off it actually is typical ammo may run ok, but drop in some ammo at the high end of the tolerance range and the fun starts.