I’m coming up on finishing my first AR-15 build and I have hit a snag… I’m having alignment trouble with the J.D. Machine Upper & Larue barrel nut. I’m using a moly based grease on the threads, I have torqued, taken lose and torqued again the barrel nut ranging from 30 to 80 foot pounds with no new results.
My question, is it safe to go above 80 foot pounds?
Also, the barrel nut comes into alignment between 20 and 25 foot pounds with using a 5-pin PRI barrel nut wrench and 1/2" Craftsman click type Torque wrench.
For this build I’m using the following parts combination.
Lower Reciver: JD Machine.
Upper Reciver: JD Machine.
Lower Parts kit: Colt.
Upper Parts Kit: Colt.
16" Barrel, Mid-Length Gas System: White Oak Armament.
Phantom Muzzle Brake: YHM.
N/M Bolt Carrier Group: Young Mfg.
Raptor Charging Handle: Rainier Arms.
Enhanced Takedown & Pivot Pin Set: Battle Arms Developement.
CASS-SA Ambi. Selector Switch: Battle Arms Developement.
Bolt Catch: Seekins Precision.
Billet Mag Release: Seekins Precision.
Trigger Assembly, SSA: Geissele.
Tele-Stock Assembly, Mil-Spec. & H2 Buffer: Cavalry Manufacturing.
Buffer Spring, Blue Spring: Tactical Springs LLC.
A2 Pistol Grip: Cavalry Manufacturing.
9" Handguard LT15-9, Free-Float: LaRue Tactical.
Post-Ban Front Sight Assembly .052 Post, Set Screw Base: White Oak Armament.
Nitrocarburized Gas Tube, Mid-Length: WMD Guns.
Carry Handle Assembly, Rear Sight 6/3: Colt.
I will post some photos once I get this alignment issue solved and I’m able to complete the build.
Thank you Folks for any and all help you can offer.
In your situation, it’s probably fine to go over 80 ft-lbs (until the barrel nut is aligned). But, what barrel nut tool are you using, and how are you aligning the torque wrench in relation to the tool?
The reason I ask is because I want to get an idea of how far the centerline of the ratchet head is from the centerline of the barrel nut, and how accurate your torque reading is.
Sorry, I missed the part about the PRI tool in your original post.
The centerline distance is correct, and having the torque wrench aligned lengthwise with the PRI tool is correct too. Since your threads are greased, your torque readings are accurate (relative to the mil-spec torque value).
I say it is fine to go until the first notch lines up past 30 ft-lbs. If you are really uncomfortable with that, you may want to lap the front of the upper receiver just a tiny bit. That will allow the barrel to tighten down a little farther with the same torque. You might want to try using something like 600-1000 grit sandpaper and a hard flat surface. This will make sure the receiver surface is trued up. I’ve never done that before, but I’ve heard of it being done successfully.
You can also use barrel nut shims, but I’ve never used those either.
Try another barrel nut. Also, set the wrench to 30 ft./lbs and then stop, see where you are at. Then tighten it slowly (assuming you have worked it a few times) until it lines up. You should be able to get it to line up correctly. Also, make sure that the barrel is seated all the way into the upper.
I have never had to lap anything on an AR to get a nut to line up. I have probably assembled somewhere close to a thousand uppers. In the military a barrel assembly comes with an FSB and barrel nut installed. I can recall maybe a few times where I had to use a different one. I think I would be wondering what’s going on and whether or something is out of spec. Something tells me there is more happening here.
IG has given you the best info… Something seems wrong, try a new barrel nut and start at 30 lbs, work it till it lines up.Take the time to look over everything again…
I have had this happen before. Lapping the receiver face squarely ever so slightly, were talking mere thousandths can get you there. I have seen uppers with a little too much anodizing in terms of thickness have this issue. Easily fixed and with very, very minimal material removal. You shouldn’t even have to lap through the anodizing on the receiver face.