Headspace on new AR build?

[68_F100]

I finished my new build. I am unsure about headspace though. I used a BCM bcg and barrel and mega billet upper. Any way to tell or anyone around indy that could check it with a gauge?

 

[mvician]

Headspace is set when the barrel extension is mounted to the barrel.
You can buy the gauges if you want to be "sure".

 

[IndyGunworks]

I agree with the above. You don't set your own headpspace if you bought a barrel with the extension already on it.

 

[gregkl]

Headspace is set when the barrel extension is mounted to the barrel.
You can buy the gauges if you want to be "sure".

I am putting together my upper this build instead of my last build when I bought a completed upper.

So I understand, what do I need to do as far as checks and measurements when I put it together? Other than alignment, torque and careful inspection of the parts prior and after assembly, do I need to do anything else?

I have my stripped upper. I still need everything else for the build.

 

[mvician]

The barrel extension comes already mounted to the barrel. The extension has a post on it the will index into the notch in the upper receiver to align it. Grease the outside of the extension and inside the upper receiver so that everything goes together smoothly. I tighten and then loosen the barrel nut three times, then tighten it one last time, check the alignment where the gastube will pass on the nut with the hole in the upper receiver. Tweak tighter if necessary to get it right. Torque range is from 30 to 90 ft pounds, anything past 30 is good if it aligns.

 

[midget]

Seeing how no one has answered your initial question here you go:
You should not have to worry about head space. I've built more than my fair share of rifles and have yet to have a problem.
If you want to check the head space, you either need to make some dummy rounds to the proper specification or buy a set of go/no go gauges. Insert the dummy round into the chamber and close your bolt onto it. If the bolt doesn't close, check your chamber for burrs/imperfections/etc and try again. If after this it doesn't close, you need to get more advanced than I can explain right now. If it does close, put your finger on the bolt carrier through the ejection port and try to move it rearward. It should have very little to no rearward movement.

I quit worrying about checking the headspace after my first build and just go straight to the range, chamber, and fire a few rounds individually.

 

[Go Devil]

Clearly, no one here has gauges that they are willing to assist with.
I posed the same request over the summer with the offer of buying a lunch, coffee, or beer.
Couldn't find a anyone with a set.

Good luck.

 

[midget]

Clearly, no one here has gauges that they are willing to assist with.
I posed the same request over the summer with the offer of buying a lunch, coffee, or beer.
Couldn't find a anyone with a set.

Good luck.

If I had a set of gauges, I would gladly loan them out. However, I haven't found a reason to spend 80$ on a set yet...

 

[gregkl]

The barrel extension comes already mounted to the barrel. The extension has a post on it the will index into the notch in the upper receiver to align it. Grease the outside of the extension and inside the upper receiver so that everything goes together smoothly. I tighten and then loosen the barrel nut three times, then tighten it one last time, check the alignment where the gastube will pass on the nut with the hole in the upper receiver. Tweak tighter if necessary to get it right. Torque range is from 30 to 90 ft pounds, anything past 30 is good if it aligns.

Thanks Mike.

 

[Leo]

Greg, check your PM's

 

[ShootnCut]

QUOTE: "I finished my new build. I am unsure about headspace though. I used a BCM bcg and barrel and mega billet upper. Any way to tell or anyone around indy that could check it with a gauge?"

If I didn't live halfway across the state I'd be happy to help you. And I agree that checking head space is a good idea. Most of the time, probably 99 times out of 100 it's not a concern. But I have to emphasize MOST.
I've been putting AR s together since the late 80's and have only had issues twice. The first time was because of a junk bolt a friend bought. It had extremely excessive head space and I wouldn't have wanted to fire that rifle. A good quality bolt fixed the problem.
The second time involved two rifles. I had purchased a Nodak lower to replace a modern lower on an A1 replica. After everything was together I had a nice matte lower with a shiny upper. Since I had a carbine with a matte upper and a shiny lower, and I couldn't just replace the complete upper assemblies, I decided to replace the upper receivers only so the finishes would match. This of course involved switching barrels on both uppers. That's when things went to hell as one had excessive headspace when I was done. Now both of these uppers had been put together originally for over 20 years and had been fired numerous times. And both checked out fine. All parts involved were good quality and not the gun show crap that used to be so prevalent years ago. Switching the carriers took care of the problem and both checked out.
Now I don't understand how the carriers would change that much as opposed to switching bolts or barrels. But that's the way it worked out. And if your headspace isn't right you have very limited options short of replacing parts. As was stated earlier there's really no adjusting to be done.
You'll probably be OK but there is always that slight possibility it could be off. I would make certain a round chambers and the bolt fully locks. (The carrier is all the way forward.) Fire one round and inspect the case for any splitting or stretching. If it looks good you are likely good to go. Compare it with any other spent case you or a friend has. If anything looks wrong then definitely get it looked at.
I'm not trying to scare you, I just want you to be aware of the fact that although you can have dozens of builds that turn out fine, (as we all have had), it can and occasionally does not turn out just right.
Good Luck.

 

[trophyhunter]

Op, if your ever in South Bend look me up I have field~go~no go gauges for most popular calibers. Anyone who endorses NOT bothering to check head space on a personal build is gambling with the PSI the round in question produces just inches from their face. (50K range on 5.56 loads)

Buy the gauges if your assembling or building rifles, what's it worth to keep your face and eyes intact!?

 

[padawan]

I have a set of go/no-go in both 5.56 and .223. I'm in the Lafayette area if someone wants to meet up.

 

[remauto1187]

If I had a set of gauges, I would gladly loan them out. However, I haven't found a reason to spend 80$ on a set yet...

Im still not quite sure why people feel they need a "set" of gauges for a brand new rifle. You would only need a .223/5.56 NO GO. That is what you are concerned about. A go gauge is essentially your factory loaded round. No blow up condition happens if the bolt wont close on a in spec round. The problems happen when a bolt closes on a in spec round and the headspace has too much space between the face of the bolt and the face of the cartridge case. Your bolt SHOULD NOT close on a NO GO gauge. If it does then you have excessive headspace and that will lead to KABOOM of your receiver/rifle. Shouldn't ever need a Field Gauge for a brand new rifle.

 

[remauto1187]

Op, if your ever in South Bend look me up I have field~go~no go gauges for most popular calibers. Anyone who endorses NOT bothering to check head space on a personal build is gambling with the PSI the round in question produces just inches from their face. (50K range on 5.56 loads)

Buy the gauges if your assembling or building rifles, what's it worth to keep your face and eyes intact!?

+1

 

[trophyhunter]

If you can close the bolt completely over a no go gauge you need to have a field gauge at that point to determine how close you are on the head space bubble to reworking the barrel and chamber or making an adjustment to a barrel extension in the case of an AR. Without a field gauge after a no-go check fail all you can do is "guess" at what to do next.

If the bolt closes on a field gauge after failing the no-go test you know for sure at that point the rifle is not safe to fire. Alternatively if the field gauge won't close the bolt but still fails on the no-go it gives you some insight as to how much case stretch your potentially dealing with and your rifle is still safe to fire. There are two entirely different schools of thought in the auto/semi auto versus hand cycled rifle bolt worlds as to what's acceptable for long term use as it relates to firing higher numbers of rounds.

I can share this with you, I built all of my rifles with close tolerances to failing no-go and passing field head-space checks. Previously fire formed brass achieves the best expansion duration and the rifle generates maximum repeatable chamber pressures that way with carefully crafted hand loads. The groups those rifles shoot speak for themselves. That's likely not a big concern for an AR-15 user but the science still applies and I'm the last person on earth interested in having my face removed by escaping chamber gas and shrapnel from a bolt explosion.

In the OP's case of an AR build .223 and 5.56 gauges are not the same, he needs to know what reamer was used to cut his chamber (hopefully the barrel is stamped with chamber cut, twist etc...)

 

[sloughfoot]

It used to be that the custom barrel makers sold you the AR bolt that they used to set headspace. They no longer do that if you are using a standard bolt. If you are using a plated bolt, they want it before they set headspace. Because they are not standard, maybe.

Just look at Kreiger's website for their statement on this manner. They explain it pretty well.

Like Midget, I don't worry about headspace on a AR. If you really are worried, fire one new factory round and check the fired brass in a case gauge.

 

[Psode27]

Its always a good idea. I always check with any (for sure non matching) mosin/Mauser/Enfield or an AK build. My AR builds I have not in the past. not saying its good practice though. Im not really a fan of that anymore though. The more I read the more I think manufacturers with AR parts suck. It turns out many 5.56 marked chambers aren't truly in spec with, well, a 5.56 chamber. Read up on that in your own time, that's a whole other issue but my next AR build I will be probably buying gauges or finding some. A chamber checker or reamer would be cool too (anyone have one?). Checking headspace, even if its "always" good is something you can do to help make sure you have a safe rifle. Might as well do all you can to limit any variables you can.
That being said, anything I build gets fired from as far away from me as possible.... . Anyone ever get questioned why you have a motorcycle helmet at a range before? Haha.

Stay safe!

 

[remauto1187]

Its always a good idea. I always check with any (for sure non matching) mosin/Mauser/Enfield or an AK build. My AR builds I have not in the past. not saying its good practice though. Im not really a fan of that anymore though. The more I read the more I think manufacturers with AR parts suck. It turns out many 5.56 marked chambers aren't truly in spec with, well, a 5.56 chamber. Read up on that in your own time, that's a whole other issue but my next AR build I will be probably buying gauges or finding some. A chamber checker or reamer would be cool too (anyone have one?). Checking headspace, even if its "always" good is something you can do to help make sure you have a safe rifle. Might as well do all you can to limit any variables you can.
That being said, anything I build gets fired from as far away from me as possible.... . Anyone ever get questioned why you have a motorcycle helmet at a range before? Haha.

Stay safe!

I have a Hornady chamber gauge and also NO GO gauges for every caliber of rifle I own. The field and GO gauge are useless to me.