Question about a loose barrel nut

[Zebra644]

Long story short I bought a new Spikes Gen 2 Billet AR-15 upper and a Noveske NSR 15 Keymod Rail and Troy Claymore. The smith at the shop who builds some quality stuff only tourqed the nut to about 30-35 lbs. I advise him Noveske says 60-80 as per that pesky little thing called the instructions. I get told it will hold at this torque value. They were extremely busy and I am not an armorer. The last time I free floated a barrel on one of these I over indexed the barrel nut and my sights went all the way right and would not co-witness thus requiring me to buy a new upper and let someone else who knew what they were doing take care of install. It was not that much of a loss, it was a Stag Arms and my very first AR to mess around with, and that was a number of years ago.

So I am trying to zero in this new upper and rail with the same lower, same Troy flips, Aimpoint and Daniel Defense barrel and it starts out at the far left and it appears as though my rear sight is going to bottom out in order to zero. The groups go from left to right and back again I am chasing the zero around. I am at an indoor range benched and resting on a sandbag. On the last string the group opens up to the size of a tennis ball, I clear the rifle and hand it to a friend to shoot and the rail twists, so loose barrel nut. I take it to another smith as I am in that part of town and you can unthread the barrel nut by hand. He follows the instructions and we end up at right about 80 lbs of tourqe for things to line up. I have plans with my wife and am unable to go back to the range until this coming weekend.

I have googled foo'd but been unable to locate if a loose or under tourqed barrel nut can casue the rear sight to allmost bottom out and or groups to jump around like that with having play in the barrel? Thankfully the other smith looked over the upper and barrel and even miked it out an all is well. Thanks in adavnce

 

[devildog83]

I'm no expert but an upper I had was the same, torqued it to 75lbs and all is now good in the world lol. As for the rear sight bottoming out I would assume that would cure the issue as well. Best of luck!

 

[Zebra644]

Update, the 80 lbs of torque fixed the problem I had the irons and optics zeroed in with 12 rounds, my groups returned to normal and everything co-witnesses fine. I have also noticed that a few other owners of Noveske NSR Rails had to have 70-85 lbs to line up and stay put. So those of you that may find this on a search hope this helps.

 

[troupe]

Someone should not be allowed to charge money for doing a customer like that.

 

[Deadshot2]

Someone should not be allowed to charge money for doing a customer like that.

This is a perfect example of why I do as much work as possible on my firearms.

With 3 AR's in the "stable" I have my own vise adapters and armorer's tool. It doesn't take that much money enable you to do your own work and get exactly what you want, when you want it, and probably a lot better quality results.


If you already have a good bench vise you can buy the tools for less than what an average "smith" will charge you for his shop time.

 

[wxl]

Most recommend 30 to 80 ft-lbs on barrel nut.

 

[sentry1]

Most recommend 30 to 80 ft-lbs on barrel nut.

The generally accepted practice amongst the local competition AR guys here is to use a minimum torque of 30 ft-lbs on barrel nuts, and then adjust upward just enough to line up the gas port opening. No more than necessary.

The first gunsmith was probably working off a similar assumption, but Noveske probably knows best what works for their specific design. Hopefully gunsmith #1 was just not up to date and will learn something new.

Also, I second the opinion on acquiring your own tools. A bench-vice and other tools are not very expensive, and in the long run are more convenient and cost-effective than running to a gunsmith everytime something needs to be done.

Caveat emptor: If you're gonna do-it-yourself, make sure you know what you're doing.

 

[Zebra644]

It's my personal rifle used as a duty rifle and I am required to have a certified armorer / smith make the corrections as I have yet to get certified, or I would fellas trust me.

 

[tipper]

Scary

 

[Deadshot2]

The generally accepted practice amongst the local competition AR guys here is to use a minimum torque of 30 ft-lbs on barrel nuts, and then adjust upward just enough to line up the gas port opening. No more than necessary.

How many of those competitors are using custom uppers and barrels?

I like to actually "bed" the barrel into my uppers when I want super accuracy. Degrease and sand the inside of the upper barrel mounting "bore". True the end of the receiver. Wax up the barrel extension and shoulder with Kiwi shoe polish. Apply a thin coating of Devcon inside the upper, insert the barrel, and tighten the barrel nut just enough to seat the extension fully inside the upper. Make sure to wax up alll surfaces that you don't want the Devcon to stick to.

To remove, use some "mule tape" (used for winchline when pulling electrical wire) tied off to the barrel with a "clove hitch". Tie the loose ends into a loop and use a "Slam Hammer" to pull the barrel loose from the upper that's secured in the vise. Might be good to have someone "catch" the barrel before it hits the floor because the "slam hammer" will take two hands.

Clean up the devcon overflow and reassemble. You won't need much more than minimal torque to keep the barrel secure as there's no more room for it to move back and forth.