AR Gas Tube?

[mpbclutch33]

Just wrapping up my first AR Build and let say it was very rewarding and fulfilling. Everything went smooth except aligning the gas tube. I torqued the barrel nut to 30 ft/lb. back off three times and to 60 ft./lb. I was not able to get it to line up perfectly. I went past a little bit and at that point I was at the 80 ft./lb. I don't know if it will be an issue or not but my question is, can I break it back down and start over or will that not make a difference? Do I need a need Barrel Nut?

 

[Bountied]

Loosen the barrel nut and start over until you get the barrel nut aligned perfectly within the specified torque range. Start at 30lb-ft and then go to the next gap in the barrel nut. I've found that you can stretch the threads on the upper and need a new barrel nut, I did it once by over tightening 90lb+. The other option I've seen people do is to strip the tooth off the nut using a file or dremel to create enough clearance for the gas tube. You really need to get the gas tube aligned correctly or the bolt carrier gas key might hit the tube and it may not go into battery 100% of the time.

 

[mvee]

Check the torque values. I think it might be ok to torque to only 35 lbs. If you still cant get it to work you could install shims, hone the receiver, or swap for another barrel nut.

 

[mpbclutch33]

Ok. Thanks for the help guys!

 

[alucard0822]

30lb-ft is the minimum torque, 80lb-ft is max, at least mil-spec, and provided everything is properly lubricated. Basically assemble the barrel and nut, grease every contact surface with aeroshell or equivalent, torque to 30lb-ft. Set the wrench to 80, and keep turning till the gas tube is lined up, if the wrench clicks before it's aligned, then back off the nut and start over, it should torque a little further each time. Proprietary barrel nuts and rail mounts might have a different procedure and torque values, and there are a couple optional steps to bed the extension in the receiver, but this is the basic method.

 

[outrider58]

This could be a big help to you and should be done before mounting any AR barrel...

 

[CSHS]

Here's a couple of videos that kind of contradict each other on torque wrench use on an AR barrel. But it'll give you something to think about. Depending on how you mount the torque wrench, your readings could be off.


https://www.youtube.com/watch?v=-UlOUP-N610

https://www.youtube.com/watch?v=ouedzeWCu9c

 

[clandestine]

Here's a couple of videos that kind of contradict each other on torque wrench use on an AR barrel. But it'll give you something to think about. Depending on how you mount the torque wrench, your readings could be off.


https://www.youtube.com/watch?v=-UlOUP-N610

https://www.youtube.com/watch?v=ouedzeWCu9c

Both are correct in regards to torque wrench use.

The first guy was talking about a 90 degree offset, BUT that is only used when there is more than an inch of offset between the torque wrench attachment and the barrel wrench teeth.

The second guy didnt offset because the barrel wrench was and torque wrench attachment were right next to each other, so no need to do an offset.

 

[clandestine]

This could be a big help to you and should be done before mounting any AR barrel...

Ill also add that the O.P. should get some aeroshell 33ms grease if he didnt use any. Sometimes that grease will give you that little bit of give you need to get things lined up within torque range.

The lower torque value is better for building a precision AR. Some rail manufacturers have different torque specs so be sure to follow them.

 

[clandestine]

Just wrapping up my first AR Build and let say it was very rewarding and fulfilling. Everything went smooth except aligning the gas tube. I torqued the barrel nut to 30 ft/lb. back off three times and to 60 ft./lb. I was not able to get it to line up perfectly. I went past a little bit and at that point I was at the 80 ft./lb. I don't know if it will be an issue or not but my question is, can I break it back down and start over or will that not make a difference? Do I need a need Barrel Nut?

Its fine to pull the nut and start over.