A lesson on QC, due diligence, and testing before modifying.

AR/M4 AR General Discussion
1

Here is the rifle in question. Lower bought in 2009 with a brand new unfired 10.5" upper. I have neither disassembled the lower, nor the upper (I did cut off the delta ring assembly and handguard cap but I didn’t remove the FSP or the barrel) A little bit of digging will tell you who made the upper, but I will keep it on the DL IAW site rules.

Everything on the rifle has been vetted - FH, optic, BCG, CH, lower, etc except the upper.

I began zeroing it at 100y with the iron sights and immediately noticed the rear sight was all the way to the left for a good zero. This was a yellow flag, but it was shooting nicely so I drove on. I got about 1.5" at 100 yards with 64gr Gold Dots for my confirmation fire - right where I was aiming. I was happy.

I turned on the T2 and started to zero that. The first 10 rounds (about 25 total so far) went ok. I was shooting high right with Wolf Gold. Adjusted the T2 down and left.

That’s when the fun started. My groups were then higher and righter. “There’s no ****ing way I adjusted that incorrectly, but let’s play the game” so I adjusted back twice the amount down and right (to compensate or any amount I might have done wrong)

This was the following target. I think it came out to be about an 18" extreme spread at 100 yards from a sandbag rest.

This was the next target with Speer Gold Dots. The highest 3 rounds were done unsuppressed which caused a POI shift upward, but the rest were suppressed. That’s about 7 MOA at 100 yards with quality ammo.

It also had a failure to fire unsuppressed as the bolt jammed the new cartridge in the neck as it was attempting to feed. For a little perspective, I have not had a failure to fire of any kind in any AR15/M16 I have shot since 2007 when I was a young Lance Coolie in Iraq buying into the “Lube attracts dirt” mantra preached by more senior (and retarded) SNCOs.

Red flag.

At that point I went home. $10 is too much money to spend on 7 MOA groups. I checked the flash hider and the optic at the range. Both were fine.

When I got home I did a more thorough inspection and found this:
https://i.imgur.com/cNo2U3Y.mp4

The barrel nut shot loose on a brand new upper. (It took me a second to realize the nut itself is loose, and if it weren’t for the anti rotation tabs/gas tube the hand guard would have unscrewed itself)

I am going to disassemble the upper tonight and retorque to spec and shoot it again tomorrow. It shot fine at first so I know the barrel is ok (assuming no damage was done by it being loose). Is there anything I should look for when retorquing the barrel to indicate it is a flaw deeper than simply low torque from the factory?

Lessons learned:
Don’t modify a rifle without testing it first (I doubt the manufacturer will help me now)
Learn how to perform your own QC and do it, because even quality manufacturers muck it up.
Test your shit before you take it someplace - if I had gone straight to a match or class I would’ve been on the sidelines.

2

Loose barrel nuts will cause this and is probably the cause. Tighten the barrel nut and re-install everything. I am going to guess this is a PSA upper since they have a track record of loose barrel nuts.

3

Your guess is actually Likely Many Times incorrect.

If I bought a PSA and this happened I wouldn’t have even made the thread. (Same for a canter FSB)

4

My guess is that it is an LMT since that was what you were painting in the other thread.

Tighten it all up and I would suggest you still contact then and at least let them know about the issue. Everyone makes mistakes and they may have just had one slip throw the cracks.

And you can always stake the barrel nut to be sure. :wink:

5

I see what you did there. Your buddy Firefly is gonna be disappointed.

6

Well hopefully it’s not Likely Many Times incorrectly gassed like many of them are.

7

Maybe some red Loctite. :rolleyes:

8

Damn…at least you got to the root of the problem hopefully without any other issues.

9

That works also. :slight_smile:

10

Are we talking Literally More Than enough gas or Less Mass Transiting through the gas system?

11

Likely More Too much gas. Many I have seen were in the high .070 range.

12

Always fire every weapon in new condition, with zero mods aside from optics (rifle).

Anything else is a potentially huge waste of time and money.

13

Brutal.

I had such a high opinion of their product for a long time

Sent from my iPhone using Tapatalk

14

Agreed. Even something as simple as stock rifle/carbine should be checked. I know one particular agency that removes handguards, gas tubes and checks barrel nuts before they are issued due to previous problems with several loose barrel nuts.

15

Less Mods Today with a brand new rifle.

16

You may already plan to do this, I would take the nut completely off the threads and take a close look at the threads and the nut to make sure everything is ok, if so torque it down.

17

It happens. My issue M4 did the same thing, I think my Company had 15 or 20 so it was a bad batch. New guy at the barrel nut torquing station at Colt I guess. Luckily happened in train up so they were all fixed before deploying.

Pro tip. Torque the barrel nut to MAX and then loosen 2 or 3 times. Then reapply a little grease (don’t forget the face of the barrel extension) and torque to finish.

18

Man, this thread brings back memories. One of my first complete AR purchases during the last administration was a lightweight profile barrel M4 from a company renown for their QC. The safety selector didn’t flip to 90-deg and they wanted the entire rifle back for inspection. Well, I didn’t want to give up the rifle, so I upgraded to a BAD-ASS ambi safety which seemed to solve the 90-deg problem. About six months later, I noticed rub marks under the right-side lever and realized that the selector core wasn’t centered between the receiver. The detent hole location was drilled out of spec, which wouldn’t be a problem for a left-side-only selector. None of my other lowers from this company had the problem and I eventually sold it.

I also have another lower from the same company with an A5 receiver extension that has a stuck bolt release. I shoot left-handed and use my trigger finger to drop the bolt but can’t do it with this particular lower out of eight ARs I own. There must be a burr or something catching when the bolt is putting pressure on it. It feels completely normal just fingering it without the bolt applying pressure to the bolt catch. It works when shooting right-handed and doing the palm slap, so I can see how not everyone would consider it a problem.

These small details probably don’t show up on any checklist and many not be caught by inspection. I guess my examples are Basic Checking Mistakes compared to your under-torqued barrel nut.

19

Let Me Tell you that these things happen and a Lot More Than that will deter me from Loving My Team.

Lessons, Mistakes, Takeaways. All part and parcel of Learning More Things.

20

Like Massive Turds