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Master Endmill Breaker
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Discussion Starter · #1 ·
I read a reply in one of the threads on AR-15.com that said the headspace on an AR is a moot point, unless the barrel and/or bolt are seriously worn out. I'm asking because I want to pick up an AR parts kit and 0% forging and I have been unable to find any headspace instructions.

I looked around and found a picture of the breech of an AR barrel and a bolt. I can't really see any way that headspace would be adjusted, short of dressing all the back edges of the lugs on the bolt. This would only increase the amount of headspace.

So here are my questions... Do you just slip in the go & no-go gauges and see if it's right? Is headspace adjustable on an AR-15? If so, how?
 

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Most military bookstores and or military book websites should have a copy of US Marine Corps Technical Manual TM 05538C-23&p/2 for sale. This is the definitive M-16/AR-15 repair guide.

HEADSPACE IS ABSOLUTELY CRITICAL OR YOU COULD BLOW THE GUN UP CAUSING DEATH OR INJURY TO YOURSELF OR OTHERS.

This manual goes into exacting detail concerning AR/M16 build or rebuild projects. The headspace gauges are readily available from a number of sources including Brownells, Bushmaster, etc.
 

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On a new AR barrel with the barrel extension installed most of the work is already done for you. The barrel extension not only sets the headspace but it also times the front sights as well. In theory if everything is manufactured to specs then it should all screw together and be headspaced. Obviously you have to check the headspace with a set of go and no go gauges and if it is not in spec then you have to figure out why. As Zoid pointed out there are several good publications out there on this, I would recommend buying 1-2 of them.
 

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As pointed out above, if you're buying a barreled upper you should be good to go.
I have built 3 AR's using Model 1 uppers, all headspaced correctly.
That being said, you should still check them before firing.

Go/No-Go gauges are cheap insurance.
 

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Master Endmill Breaker
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Discussion Starter · #5 ·
I'll most likely buy a kit that is already assembled and headspaced. I'll get a set of .223 or 5.56 NATO gauges and stick em in with the AK and Romak gauges.

What about the ones that don't have the upper assembled? It looks like the only way to get a tighter fit, is to find a bolt/barrel combination that is closer to minimum spec on both parts. I found a thread about reaming the chamber to increase headspace, but that seems extreme (at least from a novice perspective).

I did find a couple sites/threads with upper assembly instructions. Holy crap, these are simple! I know... Now that I said it out loud, my first build will take weeks and I'll have dozens of problems.

http://24.155.80.93/upper/

http://www.ar15.com/forums/topic.html?b=3&f=4&t=184499

I'll probably buy from http://www.model1sales.com/ when I'm ready. I'll probably hold off till September before finishing one of the 0% forgings. At least that way I don't have to neuter a complete upper. If the *[email protected]#$ liberals get a new ban into effect, I can always remove the evil parts later.
 

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Model 1 is a good choice.

I have built 3 AR's using their kits, other than missing pistol grip screw in one kit, (which they quickly replaced) They have been excellent kits.
 

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ZOID ZODIAN said:
Most military bookstores and or military book websites should have a copy of US Marine Corps Technical Manual TM 05538C-23&p/2 for sale. This is the definitive M-16/AR-15 repair guide.


Or download it for free and have your local Office Depot print and bind it for you.

Manual
 

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Headspacing an AR is simple. First assemble the gun, and shotgun the action (un-hook rear pin only). Use the No-Go gage, hook it on the extractor, install gage and bolt in your upper. If the lower won't close up completely, fine. If it will, you've got excessive headspace. Don't waste your money on a Field Gage, as if it fails no-go, you shouldn't shoot it. Once in a great while an AR fails the headspace check. If it does, the best fix is replace the barrel. Our armourer here at the shop did about 1,000-2,000 M16A2's (used from Regular Army), found only 2 or 3 out. He simply replaced the barrels and that was that.
 

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Nickle said:
Our armourer here at the shop did about 1,000-2,000 M16A2's (used from Regular Army), found only 2 or 3 out. He simply replaced the barrels and that was that.
Yes, it sounds like the AR lends itself to proper headspace just by the nature of its design. Plus, this being the age of CNC machining, etc., that may apply to other firearms as well.

The main thing is to check the headspace to make sure, since you definitely don't want improper headspace, but the likelihood is that your AR will have the proper headspace with the proper build.
 

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Yeah, and for what it's worth: You really only need a No-Go Gage. If it won't pass and ammo chambers fine, who cares? I've got a VZ-24 that won't pass a Go Gage. I was going to make up some brass for it special. Well, it chambers cheap surplus ammo fine, so I won't be making special brass.
 
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