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Posted: 2/13/2011 2:50:10 PM EST
You know how some barrel and upper combos can be a pain to get the gas tube holes to line up? Well I ran into a real hard case today.

Either super tight or hand tight, no in between. I'm going to swap the barrel to another upper to see if it helps. But does any one make shims that can be used to help align problem barrels?
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Link Posted: 2/13/2011 2:58:01 PM EST
[Last Edit: 2/13/2011 2:58:41 PM EST by iNeXile556]
I use a big flat diamond sharping stone to take a bit off the barrel nut. That loosens up the "Super tight" position.
I guess you could use some fine emery cloth on a nice flat surface to do the same thing. Keep checking for fit.

I'm guessing you tried the repeated tighten and loosen method already.
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Link Posted: 2/13/2011 3:08:37 PM EST
Yep, tried the tighten and loosen several times. Close but no cigar. How do you remove an even amount from the face of the barrel nut? I've installed a few dozen barrels and have never seen one this tough. Real bad.
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Link Posted: 2/13/2011 4:06:32 PM EST
I'd start thinking about lapping the upper
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Link Posted: 2/13/2011 4:17:46 PM EST
Originally Posted By Garandboy:
Yep, tried the tighten and loosen several times. Close but no cigar. How do you remove an even amount from the face of the barrel nut? I've installed a few dozen barrels and have never seen one this tough. Real bad.


You can't! This is bad advice, really bad advice.

This topic keeps coming up but people just won't listen. Where did a torque wrench come into play during surgery? Torque that nut to 30 ft lbs then tighten it to the next notch in the barrel nut. It's that simple.
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Link Posted: 2/13/2011 4:27:32 PM EST
Originally Posted By CAC01:
Originally Posted By Garandboy:
Yep, tried the tighten and loosen several times. Close but no cigar. How do you remove an even amount from the face of the barrel nut? I've installed a few dozen barrels and have never seen one this tough. Real bad.


You can't! This is bad advice, really bad advice.

This topic keeps coming up but people just won't listen. Where did a torque wrench come into play during surgery? Torque that nut to 30 ft lbs then tighten it to the next notch in the barrel nut. It's that simple.


That's part of the problem. It's the strangest thing i have seen. Line up one notch, then over 80 pounds to the next and it will not line up. Back it up to the previous notch and it's hand tight at best. It goes from super tight to loose. I can turn the barrel by hand in the receiver when lined up.

I can lap it I guess.

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Link Posted: 2/13/2011 4:52:27 PM EST
The top value is irrelevant. Just tighten it to the next notch.
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Link Posted: 2/13/2011 5:14:03 PM EST

Originally Posted By CAC01:
The top value is irrelevant. Just tighten it to the next notch.

No it's not. You go too far past that 80 ft-lbs and you'll crack your upper.
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Link Posted: 2/13/2011 6:31:26 PM EST
lap upper or try another nut. Its not like the threads on the nut are indexed to the area you grab with the wrench.
Mine was a PITA too, and I told myself next time, Im building a upper, I will get 2 or 3 barrel nuts so I can pick a better fit.
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Link Posted: 2/13/2011 6:46:42 PM EST
Originally Posted By mybronco2:
lap upper or try another nut. Its not like the threads on the nut are indexed to the area you grab with the wrench.
Mine was a PITA too, and I told myself next time, Im building a upper, I will get 2 or 3 barrel nuts so I can pick a better fit.


Damn, I keep forgetting this option.
Well done
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Link Posted: 2/13/2011 7:55:11 PM EST
Originally Posted By 458winmag:
Originally Posted By mybronco2:
lap upper or try another nut. Its not like the threads on the nut are indexed to the area you grab with the wrench.
Mine was a PITA too, and I told myself next time, Im building a upper, I will get 2 or 3 barrel nuts so I can pick a better fit.


Damn, I keep forgetting this option.
Well done


This is a YHM float tube with it's own nut. Only one I have for that type of tube. But good idea if it was a standard build. Of course I've never had this extreme issue with a factory style nut.

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Link Posted: 2/13/2011 8:02:45 PM EST

Originally Posted By Garandboy:
Originally Posted By 458winmag:
Originally Posted By mybronco2:
lap upper or try another nut. Its not like the threads on the nut are indexed to the area you grab with the wrench.
Mine was a PITA too, and I told myself next time, Im building a upper, I will get 2 or 3 barrel nuts so I can pick a better fit.


Damn, I keep forgetting this option.
Well done


This is a YHM float tube with it's own nut. Only one I have for that type of tube. But good idea if it was a standard build. Of course I've never had this extreme issue with a factory style nut.

Call YHM and ask for another nut.

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Link Posted: 2/13/2011 8:09:10 PM EST
Why do folks not post all the facts from the get go
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Link Posted: 2/13/2011 8:55:33 PM EST
There's probably nothing wrong with the barrel nut.
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Link Posted: 2/13/2011 8:58:43 PM EST

Originally Posted By Garandboy:
Yep, tried the tighten and loosen several times. Close but no cigar. How do you remove an even amount from the face of the barrel nut? I've installed a few dozen barrels and have never seen one this tough. Real bad.

With a lathe and a boring bar.
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Link Posted: 2/13/2011 8:59:50 PM EST
Are you using moly grease on it?
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Link Posted: 2/14/2011 1:43:09 AM EST
Originally Posted By ziarifleman:
Are you using moly grease on it?


This is my very first question in this sort of situation. Any decent anti-seize grease is absolutely essential, and "the right" grease pretty darn important. The "30-80 ft/lb" torque spec is based on a standard barrel nut being assembled with the appropriate MIL-G grease. The TM calls for tighten/torque/loosen/retorque if you can't get the desired number, and some people have reported repeating the process more than 10 times.

But the next issue is what YHM says about the torque spec for THAT unit. If they say "use the standard torque spec," then that's fine. They may ask for something different, based on the materials and treatment of the parts. Also, how are you connecting the torque wrench to the YHM barrel nut? That could make a difference.
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Link Posted: 2/14/2011 2:27:02 AM EST
Easiest way is what has already been said. Lap the front of the upper. I use 600 grit paper on the flat side of a large socket. Most time you will not even go through the anodizing before it will allow the notch to line up. You only have to remove a .001 to .0015.
I had a barrel extension unscrew yesterday on a DSA barrel using barrel blocks with the wrench set at 70 FT LBS. Going over the manual stated 80 LBs is not a good idea.

160$ barrel in the trash
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Link Posted: 2/14/2011 4:57:55 AM EST
Originally Posted By 458winmag:
Why do folks not post all the facts from the get go


So the thread can go 3 times longer than it needs to be.

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Link Posted: 2/14/2011 6:34:50 AM EST
[Last Edit: 2/14/2011 6:36:26 AM EST by Garandboy]
Originally Posted By BeerBender:
Originally Posted By 458winmag:
Why do folks not post all the facts from the get go


So the thread can go 3 times longer than it needs to be.



Does the type of nut really matter? I just installed an SAR, and this tube on another upper. The problem would be the same regardless of who made the nut or what rail, no? I just never ran into one this tough before.

Tell me exactly how the fact that the fucking nut is a YHM has extended this three times longer? The lapping and other advice remains the same.
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Link Posted: 2/14/2011 6:53:59 AM EST
Why not simply torque over minimum, then remove the offending nub?

Later,
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Link Posted: 2/14/2011 8:51:50 AM EST
Lapped the receiver, problem solved. Thanks guys.
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Link Posted: 2/14/2011 11:19:20 AM EST
Originally Posted By j3_:
Easiest way is what has already been said. Lap the front of the upper. I use 600 grit paper on the flat side of a large socket. Most time you will not even go through the anodizing before it will allow the notch to line up. You only have to remove a .001 to .0015.
I had a barrel extension unscrew yesterday on a DSA barrel using barrel blocks with the wrench set at 70 FT LBS. Going over the manual stated 80 LBs is not a good idea.

160$ barrel in the trash

DSA may replace the barrel for you, or have another alignment pin pressed in it for you. Cal them before scrapping it.
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Link Posted: 2/14/2011 11:53:06 AM EST
Randall at AR15barrels.com offers shims to index the barrel nut. That being said, Randall is MIA from this web site because of several questionable business transactions!!!

Link to barrel indexing shims FAQ

If you need further info on Randall, contact Aimless (site staff)
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Link Posted: 2/14/2011 12:20:54 PM EST
[Last Edit: 2/14/2011 12:30:58 PM EST by iNeXile556]


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Link Posted: 2/14/2011 12:51:31 PM EST
Originally Posted By PursuitSS:
Randall at AR15barrels.com offers shims to index the barrel nut. That being said, Randall is MIA from this web site because of several questionable business transactions!!!

Link to barrel indexing shims FAQ

If you need further info on Randall, contact Aimless (site staff)


I didn't think Randall was still in business. Just noticed in my Spikes directions that they mention shims for the SAR if you are using a piston with that rail.

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Link Posted: 2/14/2011 3:16:47 PM EST
Originally Posted By gee223:
Originally Posted By j3_:
Easiest way is what has already been said. Lap the front of the upper. I use 600 grit paper on the flat side of a large socket. Most time you will not even go through the anodizing before it will allow the notch to line up. You only have to remove a .001 to .0015.
I had a barrel extension unscrew yesterday on a DSA barrel using barrel blocks with the wrench set at 70 FT LBS. Going over the manual stated 80 LBs is not a good idea.

160$ barrel in the trash

DSA may replace the barrel for you, or have another alignment pin pressed in it for you. Cal them before scrapping it.


Nothing wrong with the alignment pin. The whole extension starting unscrewing becuase it was not tightened properly. When you use barrel blocks as the barrel nut is tighened against the barrel extension it is trying to unscrew the extension. Thats why you have the 80 FT LB max in the book to stop at.
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Link Posted: 2/14/2011 5:18:16 PM EST
Originally Posted By Garandboy:
Lapped the receiver, problem solved. Thanks guys.


Excellent. Glad to hear it was that simple. The front end of the upper itself has really well defined dimensions. Those dimensions can be altered by uneven anodizing, which can make it difficult to impossible to get the right torque. A tiny bit of lapping solved your problem, rather nicely illustrating this situation.
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Link Posted: 2/14/2011 5:19:26 PM EST
Originally Posted By j3_:
When you use barrel blocks as the barrel nut is tighened against the barrel extension it is trying to unscrew the extension. Thats why you have the 80 FT LB max in the book to stop at.

I had never made that connection, but you're right. Thanks for the educational tidbit!
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Link Posted: 2/14/2011 5:33:55 PM EST
Silly me, I thought the pin went through the extension into the barrel so it couldn't rotate out.

http://www.ar15barrels.com/making.shtml Check the third pic from the bottom.

Barrel nuts will loosen, it's the whole point of the star cuts - to stop rotation by snagging the gas tube. I doubt Stoner would go to the trouble of doing that and ignore pinning the barrel extension. If it unscrews, you lose headspace and catastrophe is imminent.

As for shims, just lap the upper, it not only squares it, the nut will rotate to line up without having to stack shims - and have it still out of square. Just Go Slow and Check Often. It doesn't take much.
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Link Posted: 2/14/2011 7:08:42 PM EST
Originally Posted By iNeXile556:
I use a big flat diamond sharping stone to take a bit off the barrel nut. That loosens up the "Super tight" position.
I guess you could use some fine emery cloth on a nice flat surface to do the same thing. Keep checking for fit.

I'm guessing you tried the repeated tighten and loosen method already.


Barrel nut?? How did you get down to the shoulder that interfaces with the barrel extension?
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Link Posted: 2/14/2011 7:43:46 PM EST
Originally Posted By tirod:
Silly me, I thought the pin went through the extension into the barrel so it couldn't rotate out.

http://www.ar15barrels.com/making.shtml Check the third pic from the bottom.

Barrel nuts will loosen, it's the whole point of the star cuts - to stop rotation by snagging the gas tube. I doubt Stoner would go to the trouble of doing that and ignore pinning the barrel extension. If it unscrews, you lose headspace and catastrophe is imminent.

As for shims, just lap the upper, it not only squares it, the nut will rotate to line up without having to stack shims - and have it still out of square. Just Go Slow and Check Often. It doesn't take much.


You should probably just stop there
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Link Posted: 2/15/2011 6:30:39 AM EST
Originally Posted By j3_:I had a barrel extension unscrew yesterday on a DSA barrel using barrel blocks with the wrench set at 70 FT LBS. Going over the manual stated 80 LBs is not a good idea.

Sounds like a better case for using the right tool for the job than advocating a torque value. You're torquing a nut in reference to the upper, the upper, not the barrel should be clamped. Barrel blocks are for installing muzzle devices.
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Link Posted: 2/15/2011 10:14:03 AM EST
Originally Posted By helotaxi:
Originally Posted By j3_:I had a barrel extension unscrew yesterday on a DSA barrel using barrel blocks with the wrench set at 70 FT LBS. Going over the manual stated 80 LBs is not a good idea.

Sounds like a better case for using the right tool for the job than advocating a torque value. You're torquing a nut in reference to the upper, the upper, not the barrel should be clamped. Barrel blocks are for installing muzzle devices.


The index pin basically locks the barrel to the upper, so you're not doing anything different from clamping the upper when you use a barrel vise. Except of course not putting all the torque on the aluminum upper and instead putting it on the steel barrel.
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Link Posted: 2/15/2011 11:11:16 AM EST

Originally Posted By helotaxi:
Originally Posted By j3_:I had a barrel extension unscrew yesterday on a DSA barrel using barrel blocks with the wrench set at 70 FT LBS. Going over the manual stated 80 LBs is not a good idea.

Sounds like a better case for using the right tool for the job than advocating a torque value. You're torquing a nut in reference to the upper, the upper, not the barrel should be clamped. Barrel blocks are for installing muzzle devices.

Army TM9-1005-249-23P shows that the barrel vise is the proper tool for the job. Actually it never even mentions an upper vise block.
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Link Posted: 2/15/2011 3:24:21 PM EST
Originally Posted By JoshAston:

Originally Posted By helotaxi:
Originally Posted By j3_:I had a barrel extension unscrew yesterday on a DSA barrel using barrel blocks with the wrench set at 70 FT LBS. Going over the manual stated 80 LBs is not a good idea.

Sounds like a better case for using the right tool for the job than advocating a torque value. You're torquing a nut in reference to the upper, the upper, not the barrel should be clamped. Barrel blocks are for installing muzzle devices.

Army TM9-1005-249-23P shows that the barrel vise is the proper tool for the job. Actually it never even mentions an upper vise block.


Neither does,
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Link Posted: 2/15/2011 3:45:42 PM EST
Upper blocks give the dreaded "My rear sight is all the way to the left". Never had but two unscrew. One was an Olympic and then this one.
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Link Posted: 2/15/2011 3:49:42 PM EST
Originally Posted By tirod:
Silly me, I thought the pin went through the extension into the barrel so it couldn't rotate out.

http://www.ar15barrels.com/making.shtml Check the third pic from the bottom.

Barrel nuts will loosen, it's the whole point of the star cuts - to stop rotation by snagging the gas tube. I doubt Stoner would go to the trouble of doing that and ignore pinning the barrel extension. If it unscrews, you lose headspace and catastrophe is imminent.

As for shims, just lap the upper, it not only squares it, the nut will rotate to line up without having to stack shims - and have it still out of square. Just Go Slow and Check Often. It doesn't take much.


You post a link to how one person does their barrels. But that is not how any factory ones I have seen are done. The pin is just pressed against the threads.

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Link Posted: 2/16/2011 6:43:34 AM EST
[Last Edit: 2/16/2011 6:53:18 AM EST by tirod]
Originally Posted By j3_:
Originally Posted By tirod:
Silly me, I thought the pin went through the extension into the barrel so it couldn't rotate out.

http://www.ar15barrels.com/making.shtml Check the third pic from the bottom.

Barrel nuts will loosen, it's the whole point of the star cuts - to stop rotation by snagging the gas tube. I doubt Stoner would go to the trouble of doing that and ignore pinning the barrel extension. If it unscrews, you lose headspace and catastrophe is imminent.

As for shims, just lap the upper, it not only squares it, the nut will rotate to line up without having to stack shims - and have it still out of square. Just Go Slow and Check Often. It doesn't take much.


You post a link to how one person does their barrels. But that is not how any factory ones I have seen are done. The pin is just pressed against the threads.



Raises an interesting question. This poster third from the bottom claims Colt and Sabre go further: http://www.weaponeer.net/forum/forum_posts.asp?TID=10825

Think about it, a barrel that unthreads from the extension basically loses it's headspace right there.
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Link Posted: 2/16/2011 3:03:48 PM EST

Originally Posted By Russ4777:
Originally Posted By iNeXile556:
I use a big flat diamond sharping stone to take a bit off the barrel nut. That loosens up the "Super tight" position.
I guess you could use some fine emery cloth on a nice flat surface to do the same thing. Keep checking for fit.

I'm guessing you tried the repeated tighten and loosen method already.


Barrel nut?? How did you get down to the shoulder that interfaces with the barrel extension?
My bad. I'm not sure where my head was at the time, even reading it now I can't for the life of me figure out just what the hell I was talking about.

I recall talking to a buddy in MI about doing this to the prop nuts on his boat because he couldn't get the lock nut down far enough to get the cotter key back in. But how the hell I transferred this conversation to a barrel nut is beyond me.

Getting old has it's moments, this may have been one of them.


"Nothing is more terrifying than ignorance in action" - Goethe, proven true November 4th, 2008

"For a people who are free, and who mean to remain so, a well organized and armed militia is their best security". - Thomas Jefferson
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