What causing gas tube to bent inside the upper receiver?

[UrbanWolf]

Second time I've seem this on ARs(not mine), the portion of the gas tube that is inside the upper gets bent. What causes this?

[TheBelly]

Improperly aligned gas block and/or barrel nut (if the nut has the kind that has the holes the gas tube needs to squeeze through).

someone will be along shortly to tell me I'm wrong and have the right answer.

[BPTactical]

Improperly aligned gas block and/or barrel nut (if the nut has the kind that has the holes the gas tube needs to squeeze through).

someone will be along shortly to tell me I'm wrong and have the right answer.

Ok Belly your wrong.
There, we don't want you getting spoiled.

Seriously though you pretty well covered it. Add bending it on installation, especially if whomever did not remove the gas block. A loose gas key may do the same.
Does the end of the tube show any indicators of the key hitting it or abnormal wear to a particular side?

[UrbanWolf]

Ok Belly your wrong.
There, we don't want you getting spoiled.

Seriously though you pretty well covered it. Add bending it on installation, especially if whomever did not remove the gas block. A loose gas key may do the same.
Does the end of the tube show any indicators of the key hitting it or abnormal wear to a particular side?

It looks like one side has more wear than the other, I met the guy at the range, he was banging on the forward assist after every 3 rounds, so i offered to take a look. He said the bolt have always had problems closing since he bought it. I figure the wears are due to the gas key wearing on the side where it bend towards during all this time he shot the gun. The gun is a Shurbmasta XM-15.

[UrbanWolf]

Ok Belly your wrong.
There, we don't want you getting spoiled.

Seriously though you pretty well covered it. Add bending it on installation, especially if whomever did not remove the gas block. A loose gas key may do the same.
Does the end of the tube show any indicators of the key hitting it or abnormal wear to a particular side?

When i did my build i stick the gas tube in the upper first and then aligned it with the hole on front sight/gas block, mine runs fine. I might i got lucky for the first build ever.

[BPTactical]

Well, I would say your initial assessment is sound, but I would find out what the issue is with the bolt/bcg.

[UrbanWolf]

Well, I would say your initial assessment is sound, but I would find out what the issue is with the bolt/bcg.

What to look for?

[TheBelly]

When i did my build i stick the gas tube in the upper first and then aligned it with the hole on front sight/gas block, mine runs fine. I might i got lucky for the first build ever.

I have only assembled one upper, so my sample size is pretty small. I started with the barrel nut, as mine had the little holes that needed aligning. I torqued it down at the lower end of the required range, then lined up the next hole (by tightening it tighter). When it started to get to where I could stick the gas tube through, I did. I saw how much the tube moved from left to right away from the centerline of the bore, as I looked down at the top of the barrel. I then took the tube out and advanced the barrel nut a TINY bit, then rechecked.

Advanced a TINY bit, THEN re checked, never backing the barrel nut off the upper receiver, ALWAYS advancing it and making it tighter. THAT is the reason my initial torque setting was on the low-ish end. I didn't want to back that nut off because I might as well just start over.

my barrel had an alignment nub on the bottom of the barrel to get the gas block lined up right. I verified that too, as any company can let a lemon slide out the door.

Check check recheck... then check again.