Gas key interference check and barrel nut alingment

[AnimalMother556]

I posted in other forums about a slightly mis-aligned barrel nut on an Armalite upper of mine. The tooth on the barrel nut does not appear to be bending the gas tube but it is touching it. I performed the test Quib posted in his how-to tutorial and am pretty sure there is no noticeable interference. I am curious as to whether or not the tube should make contact with the inside of the gas key. When pushing the stripped carrier forward with my finger, there seems to be minimal contact between the two. Gun has run fine for nearly 1k rounds.

[Quib]

As long as there is no obvious contact or binding that limits carrier travel, you should be fine. My personal goal though, when tightening the barrel nut, is to get the gas tube perfectly centered within the barrel nut teeth.

Part of gas tube alignment during firing, is the gas tubes ability to “float” in the upper receiver. This play allows the gas tube to “mate up” with the carrier key during cycling. A barrel nut that is not perfectly aligned, robs the gas tube of that much freedom of movement.

[Dutch]

I agree with Quib on his guidance to you. If there are no immediate signs of torsion, or flexing of the gas tube the situation at worst looks sloppy. If fit and funciton remain true go forth and add more K's to your round count.

Dutch

[Quib]

One other issue comes to mind, that may or may not be a problem, and this advice comes from my 25+ year aviation/aerospace background....lines chafing against other components.

The gas tube may not be binding between the barrel nut teeth and the receiver, and there may be plenty of room for freedom of travel and proper gas tube to carrier key alignment and proper operation. But one concern of mine would be the gas tube chafing against the barrel nut tooth it is resting against, and eventually causing enough of a gas leak to cause short stroking.

Again, I may be thinking into this too far, and of course without physically having the upper receiver in my hands to inspect, it’s hard to tell. But these minute attention to details are the types of simple things that in my industry can cause loss of life or damage to equipment if not corrected.

It may be excessive over thinking in this case. But for guys who rely on their weapons daily, in the defense of their lives or the lives of others, this type of attention to detail may apply here as well. I like to think so, and it is what drives me to maintain my personal weapons as I do.

[AnimalMother556]

Those were the concerns that I had as well. I don't have the tools to re-align this myself, so I wanted to know if it was that important. I know a local guy that's going to re-align it for me. Thank you, glad to be a part of this forum.

[Quib]

Always glad to help. Welcome to Weapon Evolution. [:)]

[Specialized Armament]

Here is how we align barrel nuts at SA. We obviously left off a few parts for simplicity. The pin is precision ground at .001 less than the bore of the gas key. Adjusting the gas tube may still be necessary to prevent interference between the gas tube and gas key.

http://i808.photobucket.com/albums/zz2/Specialized_Armament/AR%20Tools/ARTools004.jpg

http://i808.photobucket.com/albums/zz2/Specialized_Armament/AR%20Tools/ARTools003.jpg

http://i808.photobucket.com/albums/zz2/Specialized_Armament/AR%20Tools/ARTools002.jpg

http://i808.photobucket.com/albums/zz2/Specialized_Armament/AR%20Tools/ARTools001.jpg

[markm]

Nice! Good to see SA posting here!

[Quib]

I utilize a similar procedure, aligning the barrel nut to the receiver from the outside, using an appropriate sized drill bit.

That last pic shows really well, exactly how little room one has for alignment!

[Quib]

Mr. Elmore, while we are on the topic of barrel nut alignment and gas tube interference...... would you happen to have a photo available of a gas tube worn beyond limits from not being aligned properly with the carrier key?

An example showing the results of misalignment would be a great addition to the thread. [:)]

[AnimalMother556]

Good info guys, I should really spend more time here.

[Quib]

.......I should really spend more time here.


;)

[Specialized Armament]

A picture is worth a thousand words.

Left Side
http://i808.photobucket.com/albums/zz2/Specialized_Armament/AR%20Tools/ARTools005.jpg

Right Side
http://i808.photobucket.com/albums/zz2/Specialized_Armament/AR%20Tools/ARTools006.jpg

Compared to New
http://i808.photobucket.com/albums/zz2/Specialized_Armament/AR%20Tools/ARTools010.jpg

There is no method to adjust the tube so that there is no wear at all. This is a Colt gas tube and the wear is about as even as you will see. It is very rare that you will see one in worse condition as the rifle will usually quit running long before the gas tube suffers major damage.

-Mark

[Quib]

Thank you Sir for the addition of the photos.

[AnimalMother556]

As an update, I had the barrel nut realigned and as it turns out, the weld spring was broken. I always thought the handguards were awfully easy to remove on this particular upper. Thanks for the info and pics.