AR15 barrel loose

[TwoEyedJack]

A family member bought an AR15 from a private party and we went to sight it in yesterday. The weapon in question is an M4 clone from LAR with an A3-style upper.

We spent several frustrating hours trying to get the thing to group. Scope adjustments were random, iron sights were just as bad. We could not keep shots on the paper or even the target holder at 50 yards. I checked all the screws, made sure everything was tight and started to suspect that the scope was bad until we tried the iron sights with similar results.

Then we noticed that the barrel was loose. I suspect that the barrel nut was not torqued down properly. How hard is it to tighten this and what tools will I need? It looks like we would have to take the pin out of the front sight base, remove the gas tube, re-torque, then put the gas tube back in, etc. Is that about right?

 

[4thPointOfContact]

Basically yes, no hidden traps or anything as far as I can remember.
http://www.youtube.com/watch?v=UCxa0JJU4Iw

I would caution however, that unless you have the proper pieces to support the receiver in a vice that you can quickly turn an expensive upper into expensive trash with just the power of one arm. It could easily be worth the time/effort to give it to a 'smith as opposed to buying things that you may only use once.

 

[7.62 Solution]

Gas tube does go through the nut, you need to remove a roll pin from the front sight base to take out the tube. The issue will be having a the right tool to engage the barrel nut. There is an armore's tool and also a adaptor to fit a 3/8" torque wrench. Also might need an upper receiver fixture to hold it in a vice. 40 ft lbs of torque comes to mind then what ever more is needed to line up the gas tube. ( please check a manual). All in pretty easy with the right tools, not sure if possible without them especially if cosmetics are important.

 

[Redlg155]

Send the upper back to LAR and have them do it under warranty. If it is not under warranty I would still give them a call to have them fix it on their dime. It is apparently a QC problem on their side.

Sure, you could easily it yourself, but the aggravation of removing and reinstalling the taper pins, plus tool cost for a barrel wrench and upper block is not worth it...actually, just punch the gas tube pin out and remove the gas tube. Then retorque. Removing the FSB is not needed.

LAR's reputation is on this one, so give them a call. I could almost gurantee they make it right.
However, I will note that if the previous owner rebarreled it..all bets are off.

I have to ask this. are you sure it is the barrel and not handguard play? Test by grabbing the upper and front sight base. If you can move it side to side, then the barrel is loose.

 

[Gtimothy]

Unless you have the proper tools and receiver vice block, you're better off letting a gunsmith or the manufacturer torque the barrel nut. 80FT/LBS of torque can destroy a receiver QUICK!!!!

 

[awgrizzly]

You need a vise, a upper receiver vise block with insert, a barrel wrench, a roll pin punch and you should have a torque wrench. Trying to tighten the loose barrel nut without these can destroy the upper receiver. I don't think you would need to remove the gas block... just the tube by taking out the roll pin. It's really quite simple and could be a good educational project, but unless you were to continue with AR builds it would be a total waste to get the tools for this one time fix. Bring it to a gunsmith... he can have it fixed in minutes.

BTW, carefully check the gas tube and bolt carrier gas key. A barrel nut coming loose would invariably push the gas tube out of alignment and could easily cause damage or wear to the tube and gas key where the come together. And while you're at it make sure the key hasn't been loosened from the carrier.

 

[TwoEyedJack]

Guys, thanks for the info. Looks like we are off to the gunsmith.