Gunsmithing Barrel Nut Issue with Troy Alpha Install on AR10

[eddy]

I am installing a Troy Alpha rail on my AR10, and seeing as I do not have a vise or KAC barrel nut extension wrench/other tools, I took it to my local shop to have them install it for me. He came back and let me know that the teeth barrel nut would not line up correctly with gas tube hole on the receiver and that he would have to torque it past 90 to get it to fit correctly. He recommended that I snag some barrel nut shims and bring it back to have it fit correctly. Did some research here and elsewhere on the internets to see that there are a few different methods to making this fit correctly. My questions are: Is using shims the proper method for correcting this is? Should the timing be an issue at all with a torque range? Should I only use other methods to correct this issue? I can post pictures if needed, but I want to keep my hands off the upper because the more I put my paws on it, the more I want to grab a dremmel and say "%*(# it" and grind that tooth down.

BTW: Per the instructions, recommended torque for this is 30-50ft/lbs.

Thanks.

 

[nso123]

Put the rail on with it cocked a bit clockwise, then it rotates counter-clockwise into position. What he was probably running into was it looking like it was off because he didn't know to rotate the rail back to make it line up.

 

[sierracharlie338]

Put the rail on with it cocked a bit clockwise, then it rotates counter-clockwise into position. What he was probably running into was it looking like it was off because he didn't know to rotate the rail back to make it line up.

This be the answer. I just installed five last week on ar15s

 

[SMM123]

Normally, the nut is spun on by hand until tight. When this is done, there is usually a tooth of the nut directly in the middle of the gas tube hole (12 o'clock position) in the receiver. From this position, it will usually torque within the parameters of 30-50ft/lbs.

If the tooth is slightly left the hole when hand tightened, then the nut should be torqued to 30 and backed off three times, then hand tightened again to see if it will sit in the proper 12 o'clock position before torquing. If not, it may be possible to get it to line up at or before the 50ft/lb limit. If not, then shims are usually required.

If the tooth is slightly right of the hole when hand tightened, then shims are usually required.

 

[eddy]

NSO/Sierracharlie,
It's not an issue of getting the rail to be flush with the receiver. It is an issue with the teeth on the barrel nut blocking the gas tube port on the receiver. The AR10 Alpha rail has a proprietary barrel nut which is different than the stock AR15 one, and installing the Alpha rail on the AR15 was a dream. Once the barrel nut is in place, it was easy to install the rail and line it up correctly and tighten it down.

SMM,
I added some pics, and the tooth is covering the left side of the hole. When the guy went to install it, he put it on and backed it of 3 times, and this was still the result we got. So it looks like shims would be needed? He left it at 30ft/lbs, and that is where it sits in the pic. It is still blocking the hole. The link below is what I have found for barrel nut shims.

AR-10 Barrel Nut Shim Set - Bison Armory Store

 

[eddy]

To give some closure on this and help anyone else who may have this issue, I called Troy's Customer Service who were very helpful with the issue. Explained everything to them, and their recommendation was to torque it up to 85ft/lbs, and if this did not solve the issue, order a new barrel nut to try. The advised against using shims to fix the situation. Went back to the shop and tried it again. It had to go all the way to the 85ft/lbs in order for the teeth to line up with the gas tube. Now everything lines up and is put back together. Pics are below. Troy Alphas on both rifles.

 

[msalm]

Another option, and one that will only improve accuracy is to face the receiver a few thou. It will give a good 90 degree square surface for the barrel extension AND it will allow you to torque the barrel nut on to the proper index without popping a nut in the process.