Gas tube contact on barrel nut

[JediGuy]

General Details:

FCD URF sans FA
CMT DRT 13”
Criterion Core 13.9”
BCM .625 gas block
Midlength gas tubes - Aero and Damage Industries

It’s been probably a couple years since I assembled an upper. But I’ve done more than a few, and I don’t recall noticing this issue before. Maybe I just didn’t notice.

Issue:
The Aero gas tube clearly makes contact with the CMT barrel nut. It does not “float” over it. I grabbed the Damage gas tube that I have as an extra, and it actually was now obviously making contact than the Aero was, with some pressure.

A little googling and a Criterion video point toward bending the gas tube as a valid resolution for this.

Anyone else bend their gas tubes? Any tricks to it?

I’m looking to get the most repeatable performance I can out of this upper, so I don’t mind doing it’s. Just new to me.

[markm]

Iraqgunz used to use a large flat tip screwdriver.

[556Cliff]

First, are you sure that your barrel nut is aligned perfectly? If not, get one of these. > https://www.specializedarmament.com/...cision-ground/

Brownells has them too. They aren't as nice, but they work the same. > https://www.brownells.com/tools-clea...ignment-gauge/

Otherwise, m-guns has a gas tube bender. I'd go that route over the screwdriver method. > http://www.m-guns.com/tools.php

[JediGuy]

Iraqgunz used to use a large flat tip screwdriver.

I am not visualizing that…

First, are you sure that your barrel nut is aligned perfectly?
…

Otherwise, m-guns has a gas tube bender. I'd go that route over the screwdriver method. > http://www.m-guns.com/tools.php

The barrel nut isn’t timed, unlike a GI or some others. So impossible to be the issue.

I actually was looking at that Michigun bender last night! But it looks like it is for adjusting more within the receiver, if I’m understanding correctly. It appears that the issue with mine is further out.

[ViniVidivici]

The flat blade would be for adjusting within the upper as well.

Personally, I don't think it'll be a problem as long as your carrier mates up well with the tube. I mean, if you give it a vend to get it off the nut, it will make it dip downward inside the upper, and then you'd have to bend THAT section back up, right?

I have no problem giving the tube a slight bend, by hand, if needed for good fit though.

[556Cliff]

The barrel nut isn’t timed, unlike a GI or some others. So impossible to be the issue.

I actually was looking at that Michigun bender last night! But it looks like it is for adjusting more within the receiver, if I’m understanding correctly. It appears that the issue with mine is further out.

Ah, I get what the issue is now.

Have you tested to see if the gas tube binds up in the gas key?

[markm]

The flat blade would be for adjusting within the upper as well.

This is what I meant. I assumed that the upper was complete, or he couldn't know for sure the final position of the tube.

Isn't alignment checked with an empty carrier and the upper half inverted? It's been a while for me.

[JediGuy]

I was about to install the gas tube, and that’s when I noticed that with the gas block aligned and gas tube straight into the upper receiver, the bottom of the tube was impacting the barrel nut.

[556Cliff]

Isn't alignment checked with an empty carrier and the upper half inverted? It's been a while for me.

That's the final check, to make sure the carrier freely slides all the way forward with little to no resistance and slides out under it's own weight when the upper assembly is tipped rearward.

[556Cliff]

I was about to install the gas tube, and that’s when I noticed that with the gas block aligned and gas tube straight into the upper receiver, the bottom of the tube was impacting the barrel nut.

So is the barrel nut actually partially blocking the hole for the gas tube into the receiver?