Lets talk AR headspace..

[porscheboy]

Got a quick question, when assembling an AR upper is it crucial to check for headspace? If so is there any way to avoid this? For example, could i just buy the barrel and bolt from the same manufacturer? Such as Daniel Defense or YHM?

-Thanks

 

[TexasRifleman]

Most of the time on the AR's you will be fine since the bolt locks into the barrel directly unlike many firearms where the barrel screws into a receiver then the bolt locks into that. You can buy a set of GO/NO GO gauges cheap (or better yet borrow some) to make sure, then good to go.

 

[taliv]

but yes, you can also buy bolt/barrel combos from many vendors. white oak, denny's, and lots of others sell them as a matched pair.

 

[Quentin]

You can also measure the length of spent brass and see if it remains in spec. If the brass is good at least you know that you don't have too much headspace. That's the only test I've done on my two ARs but if I could get my hands on gauges I'd sure check headspace.

 

[HOLY DIVER]

i tried 2 send my new BCM build to Bill Springfield and have him check the headspace..he asked BCM barrel BCM bolt? i said yes he said u got a better chance of hitting the lotery than having a headspace issue with new BCM parts

 

[benzy2]

My question is, what if headspace is too much or too little? Then what do you do short of send it back?

 

[cfullgraf]

In my opinion, the headspace should be checked on a new barrel and/or bolt for an AR. Out of tolerance headspace can cause inconvenience at a minimum to being unsafe.

Manufacturing procedures today are pretty good and tight tolerances can be easily met such that most bolts probably will be within tolerance with most barrels. But it is possible to have a bolt and barrel at the extremes where the headspace is out of spec.

Gauges are about $20-$25 or so each, you need two. A good expense if you build a number of ARs.

Generally, when I buy a new barrel, I buy it with a matched bolt and avoid hunting for a correct bolt.

benzy2, if the headspace on a AR is out of spec, one can try other bolts to see if that corrects the problem. If the headspace is too short, the chamber could be reamed some more.

 

[benzy2]

But if the bolt is to spec and the barrel has too much headspace then what? If it's too little it would be an easy enough fix. If the bolt was the problem, again, easy enough fix, but what if it's too much and due to the barrel? I personally have always bought bolts headspaced to the barrel they were going in at the same time and haven't worried about it. But I always wondered what someone did if they found it to be out of spec, especially with the barrel having too much headspace with a spec bolt.

 

[porscheboy]

Awesome guys, so I guess my question now is... Can I just buy a YHM barrel and a YHM bolt carrier assembly and be okay with headspace ?

 

[Onmilo]

ALWAYS check headspace prior to firing any rifle.
While the M16 type rifles will generally headspace to safe levels with a great majority of bolt and barrel combinations, there is always the possibility of receiving a short chambered or non finish reamed barrel that managed to slip through quality control.
I have had two barrels arrive with this condition.

If a barrel chamber is chrome lined, there is nothing you can do other than ship it back.
A non chrome lined chamber can be finish reamed to safe dimensions but you would need special tools to do this work yourself.
Again, for the average hobby builder, your best option is to return the barrel for replacement.
A short chambered barrel also indicates the barrel has not gone through any sort of proof firing also.

Never assume everything is good to go, always check prior to firing any firearm.

 

[Z-Michigan]

You can actually ream chrome-lined chambers, read here:
http://www.m-guns.com/tools.php

However, on a new rifle or barrel I would absolutely send it back for replacement with one in-spec.

I have assembled several ARs without checking headspace and haven't yet had a problem. However, I finally got myself a 5.56 no-go gauge, which indicates excessive headspace - the thing that will cause you risk. Inadequate headspace will show up as difficult or impossible chambering, so I didn't feel the need for a go gauge. There is a slight difference in headspace between .223 Rem and 5.56 NATO, so be sure to get the right gauge for the chamber you are supposed to have.

 

[TonyAngel]

This is one of those things where someone read something on the internet and it just got them all worked up for nothing. If you are buying quality parts from a quality vendor, as B.S. said, you have a better chance of hitting the lottery than having a headspace issue. Checking headspace is more important in terms of maintenance when checking for worn parts or maybe installing a custom barrel extension or something like that. If you are going plain vanilla, it's not a concern.

About all I check for is excessive headspace with a field gauge. If I have a rig where I can get the bolt to close on a field gauge, I'll replace the bolt and check again. This is only after the rifle has seen MANY thousands of rounds.

 

[Welding Rod]

Side note: Some manufacturers hold pretty tight clearances on head space and some are looser. The "milspec" guns may be looser to behave more reliably when they are not properly maintained, but they may also stretch your brass more than necessary. Some thing to consider if you reload.

 

[Z-Michigan]

The "milspec" guns may be looser to behave more reliably when they are not properly maintained, but they may also stretch your brass more than necessary. Some thing to consider if you reload.

And on that note, I recently purchased a 5.56 testing chamber gauge (not a headspace gauge, but a gauge to measure whether the leade is cut to 5.56 NATO specs or is tighter, telling you whether or not it's a good idea to use 5.56 NATO ammo). The gauge is not designed to measure overall chamber dimensions, but it is cut to basically the size of a 5.56 case, so it strongly hints at overall chamber dimensions. I found that a new Daniel Defense hammer-forged barrel was not only at or above the required leade dimensions, it also had a chamber big enough that the gauge practically rattled inside it, which was not the case with any other barrels I tried, including two that were also definitely cut to the 5.56 NATO spec. Just demonstrating your point.

The gauge I refer to is found here:
http://www.m-guns.com/tools.php