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Posted: 5/26/2003 6:52:51 PM EDT
Hey guys.

Though I may have seen a simular thread but can't find it anywhere, so please excuse if it's a repeat.

First time doing a barrel install. I am installing a PRI carbon fiber tube on my upper, but I have a problem with the torquing.

I have put moly grease on the threads. Even after doing the 3 times 30 ft/lb torque routine, at my 30 ft/lb torque point I am just pass a hole and can't make it to the next barrel nut hole before reaching 80 ft/lb.

Is it suffering threading incompatability... too much grease... any suggestions on remedy or solution ??

Thanks
Link Posted: 5/26/2003 8:15:21 PM EDT
Ah.... barrel torque [beathorse] Tear that barrel install page/section out of the TM and round file it and than tighten to next hole !
Link Posted: 5/26/2003 8:38:16 PM EDT
Get another barrel nut and try again. The thread engagement will be ever so slightly different in relation to the lugs. Now for the tough part: Replacing the barrel nut will require you to remove your sight base! It might be more convenient to replace the upper, actually. And a new upper might have a better match in terms of thread engagement. CJ
Link Posted: 5/26/2003 10:34:58 PM EDT
There is a work-around if you have reached 81 Lb.-Ft. of torque on the nut (you can go up to about 90 if you're close to proper alignment usually without damage or stripping of receiver threads). I have had to do the following a couple of times when another barrel nut was not available. This must be done carefully and with caution to prevent damage to the receiver. 1. Take a 6" square piece of new 320 Wet-or-Dry and lay it on an EXTREMELY smooth and flat surface (a sheet of glass works great). 2. Wet the abrasive side of the paper with WD-40. 3. Take your stripped upper receiver and place it vertically on the paper with the opening for the barrel facing down. 4. Grip the barrel nut threads between your thumb and index finger on opposite sides. 5. While applying a light but constant pressure against the abrasive, move the receiver in small figure "8" motions while supporting the paper with your free hand. 6. You are basically "lapping" the surface where the shoulder of the barrel extension seats against the receiver. 7. Lap the surface until the black anodizing is gone and bare aluminum shows through. 8. Removing the anodizing will "shorten" the receiver about .003". This will usually be enough to torque the barrel nut to the next gas tube notch before reaching the 81 Lb.-Ft. torque limit. 9. Try the 3-times torquing process and see what you get for gas tube alignment. Be sure and use some kind of anti-sieze lubricant on the receiver threads and on the front side of the barrel extension shoulder. 10. Repeat steps 3 through 9 until you reach the next gas tube notch. You will not need to remove much material. If you are a klutz working with your hands don't even try is procedure, you may ruin your precious receiver. However, it is easy to do and the results are perfect. Don't take off too much material. Keep the receiver in constant contact with the abrasive while lapping. Use even pressure with both fingers to keep the lapping of the shoulder parallel to the original surface. This will NOT affect headspace or operation of the rifle in any way. The absence of anodizing on the forward surface of the receiver is not going to cause any problems either. Good luck!
Link Posted: 5/27/2003 12:29:19 AM EDT
My last barrel installation required torque beyond the high limit. Next time I am going to shorten the receiver front edge as Russ4777 suggested. I would not remove .003" though. The barrel nut thread pitch is about .055". With 20 notches in the nut, a change of only .0027 will advance the nut by one whole notch (which would put you right back where you started). Removing 1 or 2 thousanths should do it. Rotating the receiver occasionally by 1/4 turn will help remove metal evenly. Also, don't use regular window glass which may (and usually does)have ripples. Plate glass has a ground surface.
Link Posted: 5/27/2003 4:44:38 AM EDT
don't worry about it. just tighten it to the next slot on the barrel nut. don't take any metal off of your receiver you won't screw anything up. i've done it many, many times and have never stripped a receiver.
Link Posted: 5/27/2003 3:26:32 PM EDT
I didn't realize that the pitch was so small. I had added some grease on the back of the nut where it contacts the barrel extension, that grease may cause enough thickness to effect the torque. I will clean up the barrel and nut, then I will try again. Replacing the nut is impossible, it was hard enough getting the PRI gear exported and as far as the upper, it's new but I already installed the assist and door. I would loose some money trading it in. Good suggestions though, and probably the best way to go, however if removing the grease doesn't help I may try lapping the front of the receiver threads. Thanks for the info and ideas.
Link Posted: 5/28/2003 10:40:45 AM EDT
Originally Posted By Russ4777: There is a work-around if you have reached 81 Lb.-Ft. of torque on the nut (you can go up to about 90 if you're close to proper alignment usually without damage or stripping of receiver threads). I have had to do the following a couple of times when another barrel nut was not available. This must be done carefully and with caution to prevent damage to the receiver. 1. Take a 6" square piece of new 320 Wet-or-Dry and lay it on an EXTREMELY smooth and flat surface (a sheet of glass works great). 2. Wet the abrasive side of the paper with WD-40. 3. Take your stripped upper receiver and place it vertically on the paper with the opening for the barrel facing down. 4. Grip the barrel nut threads between your thumb and index finger on opposite sides. 5. While applying a light but constant pressure against the abrasive, move the receiver in small figure "8" motions while supporting the paper with your free hand. 6. You are basically "lapping" the surface where the shoulder of the barrel extension seats against the receiver. 7. Lap the surface until the black anodizing is gone and bare aluminum shows through. 8. Removing the anodizing will "shorten" the receiver about .003". This will usually be enough to torque the barrel nut to the next gas tube notch before reaching the 81 Lb.-Ft. torque limit. 9. Try the 3-times torquing process and see what you get for gas tube alignment. Be sure and use some kind of anti-sieze lubricant on the receiver threads and on the front side of the barrel extension shoulder. 10. Repeat steps 3 through 9 until you reach the next gas tube notch. You will not need to remove much material. If you are a klutz working with your hands don't even try is procedure, you may ruin your precious receiver. However, it is easy to do and the results are perfect. Don't take off too much material. Keep the receiver in constant contact with the abrasive while lapping. Use even pressure with both fingers to keep the lapping of the shoulder parallel to the original surface. This will NOT affect headspace or operation of the rifle in any way. The absence of anodizing on the forward surface of the receiver is not going to cause any problems either. Good luck!
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Couldn't you do the same thing with the nut?
Link Posted: 5/28/2003 12:01:05 PM EDT
No
Link Posted: 5/28/2003 12:17:40 PM EDT
Oh ya, The collar inside is what bears on the barrel extension. Never mind. Had a brain fart.
Link Posted: 5/28/2003 7:59:40 PM EDT
[Last Edit: 5/28/2003 8:02:35 PM EDT by Homo_Erectus]
tangeant is the only one here to get it right. The others haven't figured it out yet that they really don't need to torque their barrel nuts. Someday they may finally come to the realization that the upper receiver is not a stressed member and doesn't need to cranked down on using all sorts of weird rituals, magic grease, multiple tightenings and loosenings, waving dead chickens in the air, dancing naked in the moonlight, etc. Here's what you want to do - Throw away the torque wrench and replace it with a breaker bar. Spin the barrel nut on hand tight. Then turn it until the next gas tube notch lines up. Install the gas tube and go shooting. I wonder how many receivers have been stripped, barrel nuts rounded, and knuckles bashed because someone decided to blindly follow a bunch of instructions that don't make sense. Remember, the same people who gave you the sacred TM also published books for troops on stuff like how to walk, tie your boots, and take a dump. Seriously.
Link Posted: 5/29/2003 6:52:25 AM EDT
Too loose barrel torque effects accuracy....
Link Posted: 5/29/2003 10:43:33 AM EDT
That's a myth parroted by people who don't understand how ARs work. As long as the rear sight isn't flopping around (in relation to the front sight), barrel nut torque is not important. What I really hate to see are people like Furet who are scared that they can't mount a barrel, am using the wrong grease, have to tighten & loosen the nut several times, and still can't seem to get everything right. This is not only a huge waste of time and effort, it can actually damage the upper receiver threads, the barrel nut, and/or your knuckles. The first time I tried to mount a barrel, I had the same problems. I called up a friend of mine who is a wise and experienced US Army armorer (ret.). When he got done laughing at me, he suggested I throw away the torque wrench. His exact words were "Watch barrel nut, NOT the wrench!!" Mounting an AR barrel is an easy operation that should take you about 10 minutes. If you're going through all these gyrations freaking out about torque and grease, you're doing it wrong. But it does give us something to laugh at. [:D]
Link Posted: 5/29/2003 11:47:48 AM EDT
[Last Edit: 5/29/2003 11:51:02 AM EDT by XM777]
Originally Posted By Homo_Erectus: Spin the barrel nut on hand tight. Then turn it until the next gas tube notch lines up. Install the gas tube and go shooting.
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LOL, I've installed close to fifty barrels using this procedure. I have never even tried using a torque wrench. Doesn't seem to be a problem because depending on the quality of the barrel, these guns routinely shoot inside an inch at 100yds. [added] And no, I don't use a torque wrench to install a flash suppressor or stock nut either [:)]
Link Posted: 5/29/2003 1:27:49 PM EDT
Ok ok stop laughing at me... I have never been one to follow instructions, but I consider this a bit more serious business then assembling my IKEA furniture. I will try the hand tight then tighten to next hole routine. As a note though, the next hole after hand tight gives me about 20 ft/lb and the one after that needs about 90-95 ft/lb, so if I understand this right 20 ft/lb should not cause a problem but 90 ft/lb will ?? Thanks
Link Posted: 5/29/2003 2:12:19 PM EDT
Originally Posted By Furet: Ok ok stop laughing at me... I have never been one to follow instructions, but I consider this a bit more serious business then assembling my IKEA furniture.
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Not really laughing - just giggling a little. [:)] Don't worry, we all go through this on our first barrel job. But once you do it, you'll realize just how easy it really is and wonder why everyone makes such a big deal out of it.
I will try the hand tight then tighten to next hole routine. As a note though, the next hole after hand tight gives me about 20 ft/lb and the one after that needs about 90-95 ft/lb, so if I understand this right 20 ft/lb should not cause a problem but 90 ft/lb will ??
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Go with the first hole - 20 ft-lbs. is just fine. If you gotta jump up and down on the torque wrench to get it up to 90 ft-lbs., that's definitely too much. After you mount the barrel and test fire it, be sure to post an update and let up know how it works!
Link Posted: 5/29/2003 6:14:39 PM EDT
Well it looks like Homo and XM777 need to plant a bigger shade tree out behind the barn to work under. Perhaps the sun has fried their brains. The people that engineered the fine weapons we all love so much aren't morons. There is a reason that torque specs exist. That reason is not to ignore them! There is only so much design margin that can be comsumed before failures occur. I hope that their ARs have treated them well in terms of reliability. As an experienced aircraft mechanic very much used to the application of proper torque specs, I don't think I would feel too comfortable flying in an airplane maintained by Homo and XM777.
Link Posted: 5/29/2003 6:46:56 PM EDT
[Last Edit: 5/29/2003 6:55:05 PM EDT by XM777]
Originally Posted By Russ4777: The people that engineered the fine weapons we all love so much aren't morons.
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Gotta agree with you there but somehow I just don't see Gene Stoner lapping the front face of a upper receiver [whacko] As far as reliabilty goes, most of the barrels I refer to were M-16's built while working for J. Ciener during the '80s. They ran slick as owl shit and I never heard a single complaint.
Link Posted: 5/30/2003 10:22:02 AM EDT
Originally Posted By Russ4777: Well it looks like Homo and XM777 need to plant a bigger shade tree out behind the barn to work under. Perhaps the sun has fried their brains.
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You can call me Rex. [:D]
The people that engineered the fine weapons we all love so much aren't morons. There is a reason that torque specs exist.
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Sorry, Russ4777 (are there really 4776 other Russes on this board?[:)]), but you're "mixing your morons." Your precious torque spec was [b]not[/b] written by Gene Stoner. Rather, it's a product of the Military. You have to keep in mind that these instructions were written to be fool proof, because fools may be working on these guns and need directions so detailed and so specific that even you could follow them. [:)]
That reason is not to ignore them!
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And this is the military mindset - forget common sense, forget past experience, forget any previous training, forget thinking for yourself and do it [b]Our Way[/b]. Whether it's building guns, walking, putting on your pants, eating, etc., it doesn't matter - this is the way We want you to do it. Some people like Russ4777 feel more comfortable in this type of environment, blindly following arbitrary directions with no rhyme or reason. I don't. Occasionally I like to think for myself. And that's what Russ4777 and his ilk find so threatening. I think what bothers me so much about this topic is people fail to understand and appreciate the true genius of Stoner's original design. If they did, then they'd see that the TMs are full of mistakes and were written by people who were still thinking along the lines of the M14. But the AR is a totally animal.
As an experienced aircraft mechanic very much used to the application of proper torque specs, I don't think I would feel too comfortable flying in an airplane maintained by Homo and XM777.
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We're talking about tightening one single nut. Sorry, but this isn't rocket science. And anyone who has any inkling about how an AR really works can easily see the folly in following this weird and mysterious procedure. Personally, I don't know why some people are so hung up on how to tighten a nut. They are making this much harder and far more complicated than it needs to be. Russ4777 - chill out, dude. It's not that hard. It's one nut that's not under any stress whatsoever. Tighten it and get over it. Furet - tighten your barrel nut/handguard tube until the next gas tube notch/hole lines up. It'll work fine and you'll be happy with the results. Reply back here and let us know how it works. See, wasn't that easy? [:D] You're welcome. Your pal, Rex
Link Posted: 5/30/2003 11:14:38 AM EDT
I tried it your way,hand tight, then next hole.. It took about 200 rounds, and I could move the nut by hand....... I tighten, then backoff,then tighten again, do that a couple of times,don't have/need a torque wrench.. I believe it is a heating and cooling issue, not stress.... I shoot service rifle/match guns. If they won't shoot under 6 in. at 600 yds, they are tent pegs.
Link Posted: 5/30/2003 12:49:31 PM EDT
Originally Posted By sharpshooter2: I tried it your way,hand tight, then next hole.. It took about 200 rounds, and I could move the nut by hand.......
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The only gun that ever did this to me was a factory Colt. After about 1000 rnds. the barrel nut was loose. I cranked the nut over to the next notch and it's been fine ever since. Sounds like you need to go one more on yours.
I tighten, then backoff,then tighten again,
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Definitely not my way. You should always tighten until the next notch lines up, then leave it there. If you're backing the nut off then you're doing it wrong. Your pal, Rex
Link Posted: 5/30/2003 1:01:31 PM EDT
As of yesterday, I have it hand tight + a bit more, gives about 15-20 ft/lb. I will know easily enough if the nut gets loose, cause my forend is indexed and tightenned to the barrel nut, so if things get loose so will my forend. But depending on how it goes I may tighten to 90 ft/lb. Rex: Thanks you! [:)] No clear cut answer or technic, isn't AR great, so many ways to accessories and build.. [:)] Rodney
Link Posted: 5/30/2003 5:42:03 PM EDT
Originally Posted By Russ4777: Well it looks like Homo and XM777 need to plant a bigger shade tree out behind the barn to work under. Perhaps the sun has fried their brains. The people that engineered the fine weapons we all love so much aren't morons. There is a reason that torque specs exist. That reason is not to ignore them! There is only so much design margin that can be comsumed before failures occur. I hope that their ARs have treated them well in terms of reliability. As an experienced aircraft mechanic very much used to the application of proper torque specs, I don't think I would feel too comfortable flying in an airplane maintained by Homo and XM777.
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Aircraft mechanic huh ... Do you torque hyd b-nuts ? what do you do when you can't get a torque wrench on a nut and the TO/ manual specs a torque...You do what any AC mech does and tighten just tighten it ! The TM is just a guide and if your not a mil armorer " who for the most part also think that the torq procedure is a joke " there is no reason to follow it. If you actually look at there use of torque wrenches the TM is Wrong, to get 80 ftlbs torque you have to turn the GI wrench 90 degrees to the torque wrench. Having it strait ADDS Torque above wrench setting ....Any real Torque wrench wizard would catch that mistake... I was issued a M16 with a loose barrel once, you could hold the upper and the muzzle would wiggle side to side 2". I shot it at a KD qualification course and still made ex with points to spare. The rifle ran just fine just had to keep the same sling tension !
Link Posted: 5/30/2003 7:02:39 PM EDT
Tangeant - My understanding of the procedure is that the nut is not actually torqued at 80 ft/lb, but when you use the wrench and torque bar together you tighten until the torque bar says 30-80, what actual nut torque that translates into is anybodies guess. Having e-mailed Paul @ MSTN, he says Colt will actually go up to 150 ft/lb, if >80 ft/lb is required MSTN will try a different nut so as to end up with a reasonable torque level between 35-80 ft/lb. Final procedure I did, I torqued it to the next nut hole above 30 ft/lb, which was about 95 ft/lb. It's damn tight, I installed the barrel a couple of times to try and lower the torque level, I almost pulled my vise off the bench (must say it's only screwed into 2 pieces of 5/8 ply-wood)
Link Posted: 5/30/2003 7:22:58 PM EDT
Well yes and no. Depending on how you put the torque wrench in you can add about 3" (.25' added to the length of your bar). That's an extra amount of force but usually not that significant. If your torque bar is 18", you've added 3". Your total lenght is now 21". When you put 80ft-lbs on your bar what you really have is closer to 93 ft-lbs. 35 would have been closer to 42. You may have been good to go at the first hole.
Link Posted: 5/30/2003 8:44:38 PM EDT
[Last Edit: 5/30/2003 8:49:11 PM EDT by Furet]
Halfcocked - What I am saying is that the 30-80 ft/lb spec is based on using the wrench and torque bar, meaning that the actual torque applied to the nut will be higher. That said the 30-80 is a relative torque spec and not an absolute nut torque value. The TM specifies "torque is measured when using wrench and torque bar together", to me that means that the 30-80 range must be determined when using that combination of tools, which would take into consideration the extra 3" added by the wrench. Just IMHO. Since the opinion of some military personel and others is that TM procedures are to be no brainers and most likely conservative in nature, based on that I would accept Colt's position on 150 ft/lb torque limit as the true limit. I have a real bad combination of nut and receiver, hand tight brings me just before a hole, torquing to that hole gives me only ~15-20 ft/lb and the next one is 90-95 ft/lb. That first hole does not feel very tight, and I would worry about the heat<->cold effect on maintaining a snug fit in the receiver. Having torqued it to 95 ft/lb and removing the barrel a few times has not effected the threads, because that first hole is always indexing at the same spot, I would assume that damaging threads would cause changes in the initial torquing scheme.
Link Posted: 5/31/2003 8:17:25 PM EDT
Originally Posted By Homo_Erectus:
Originally Posted By sharpshooter2: I tried it your way,hand tight, then next hole.. It took about 200 rounds, and I could move the nut by hand.......
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The only gun that ever did this to me was a factory Colt. After about 1000 rnds. the barrel nut was loose. I cranked the nut over to the next notch and it's been fine ever since. Sounds like you need to go one more on yours.
I tighten, then backoff,then tighten again,
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Definitely not my way. You should always tighten until the next notch lines up, then leave it there. If you're backing the nut off then you're doing it wrong. Your pal, Rex
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Called Colt over 30 years ago on this very issue. Tech I spoke with said they basically NEVER went over 35 lbs, and that anything over 15 lbs was fine. Every time I see one of these "tighten-loosen three times" posts I have to laugh. What an absolute joke; but if it makes the obsessive/ compulsives on the site happy to put extra wear on their aluminum uppers, who am I to complain. Sorry guys, hand tight,and then either one or two scoops beyond is all you need---but if it makes you happy to make it a major production, it's OK with me. Oh, while I'm at it, you don't need all that fancy, expensive action/barrel protection crap either. I wrap for or five layers of electrical tape around the upper and C clamp it to the work table. Works every time. If you want to make "shade tree mechanic" cracks, it's OK with me. Having just finished 6 years as armorer for the security unit at a large federal agency, doesn't bother me at all. None of the people whose weapons I maintained and repaired ever had a failure in any weapon I ever worked on, and that's the only criterion I care about[:D]
Link Posted: 6/2/2003 11:57:22 AM EDT
Don't bother with the tighten/loosen stuff, just do it up tight enough to the next nearest hole, and if you're worried about it being too tight, add some loctite, and with the gas tube installed it'll not move far anyway from the lesser setting. The manual says 'minimum 35ftlb' not exactly 35ftlb, but it'll not work loose with some loctite blue (242 if my memory serves me) and a lot less initial torque.
Link Posted: 6/10/2003 7:41:00 PM EDT
Would the fellow who contacted me about this issue please IM me again? Somehow I hit the delete button before I read the email. Thanks. A Free Man
Link Posted: 6/10/2003 10:18:57 PM EDT
The proper way to use a torque wrench, if you can't put the nut directly over the pivot point, AKA a socket, is to put your torque wrench at 90 degrees to your armorer's wrench. That way you aren't adding a length to your torque. Torque is a translatable force. [rolleyes] You torque Nazis do know that the amount and type of grease does affect the stresses in your assembly as much as your indicated torque does, don't you? I havent' heard that issue talked about. I suppose all good aircraft mechanics know about that.
Originally Posted By Russ4777: Well it looks like Homo and XM777 need to plant a bigger shade tree out behind the barn to work under. Perhaps the sun has fried their brains. The people that engineered the fine weapons we all love so much aren't morons. There is a reason that torque specs exist. That reason is not to ignore them! There is only so much design margin that can be comsumed before failures occur. I hope that their ARs have treated them well in terms of reliability. As an experienced aircraft mechanic very much used to the application of proper torque specs, I don't think I would feel too comfortable flying in an airplane maintained by Homo and XM777.
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Thank you, Homo Erectus, for taking up the cause with your excellent posts. BTW, what is the design margin involved here? Why do you think the specific torque specs are mentioned? I have a few guesses. I worked in Nuclear Power for years. There is such a thing as a "calibrated arm" technique acceptable for nuclear and subsafe work. It ain't all shade tree work. There is a difference between Bubba gunsmithing and knowing what is critical and what is not. The barrel nut is there only to keep things together and it is not a safety issue how loose or how tight it is. I pay much more attention to the lug nuts on my truck than my AR barrel nut.
Link Posted: 6/11/2003 7:21:14 AM EDT
[Last Edit: 6/11/2003 11:33:59 AM EDT by Homo_Erectus]
Originally Posted By pogo: BTW, what is the design margin involved here? Why do you think the specific torque specs are mentioned? I have a few guesses. I worked in Nuclear Power for years. There is such a thing as a "calibrated arm" technique acceptable for nuclear and subsafe work. It ain't all shade tree work.
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From what I've seen reading literally hundreds of TMs and FMs, I think the Torque Spec was created specifically because you can't teach the "calibrated arm" in a military setting. The instructions have to be written so specifically that anyone who's never even seen an M16 before can follow the step-by-step directions and complete the task. If you included something like "tighten the barrel nut until it feels right" you'd get everything from the private who spun it hand tight and backed it off 3 turns to the sergeant who used an 8 ft. section of galvanized pipe for leverage and then got his whole platoon to lean on it. Playing with torque wrenches and barrel nuts has shown me that there's only one notch that lines up within the torque spec. I think they figured out that the maximum torque on an upper receiver should be no more than ~80 ft.lbs. and that each gas tube notch is good for ~50 ft.lbs., so they set the initial torque at 30 ft.lbs.
There is a difference between Bubba gunsmithing and knowing what is critical and what is not. The barrel nut is there only to keep things together and it is not a safety issue how loose or how tight it is. I pay much more attention to the lug nuts on my truck than my AR barrel nut.
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EXACTLY!!!!! The upper receiver on an AR is not under any stress. Basically it's merely a rear sight mount to the barrel. How many people get upset about the torque on their rear sight mount? In the upper receiver's other role as a recoil guide, there is still no stress. In fact, the buffer tube suffers several orders of magnitude higher stress during firing, yet no one freaks out about torquing it down. The main reason I'm such an Anti-Torque Nazi is not because I'm protesting against The Establishment or feel that ARs should be built with barrels flopping around loose. It's because the way the TM is written it seems to put WAY TOO MUCH importance on the reading on the torque wrench, so much so that first time builders get fixated on this and it stops their project dead in it's tracks. Every time I see someone post here that they've sucessfully built an entire rifle but can't complete it because even though they used the right grease and tightened and loosened the barrel 47 times while staring at the read-out on the torque wrench they still can't seem to get the right number, it makes me want to slap these people up-side the head and scream "It's one fricken nut!!! Tighten it down and forget it!!!!" The first time I tried to mount a barrel, I went through the exact same thing. So I called a friend who was an US Army armorer in RVN and he laughed at me. His exact word were "Watch the barrel nut, not the wrench. Turn it until until the notch lines up and forget it." And barrel mounting has been easy ever since. [:D] [Edited to ficks speling misteaks.]
Link Posted: 6/11/2003 8:40:25 AM EDT
[Last Edit: 6/11/2003 8:42:11 AM EDT by Yojimbo]
Excellent thread guys! I learned a lot, seems like barreling an upper doesn't require the super secret magic dance! [:D] shamayim, Please, for us AR gunsmith retards[;)], could you describe in more detail how you c-clamp a receiver to a work bench. I think I understand what you are saying but where do you place the c-clamp on a the flat top, how about on a A2 receiver? Do you hang the threaded portion over the table? Other than the electrical tape is there any other considerations in order to avoid damaging the receiver?
Link Posted: 6/11/2003 4:05:28 PM EDT
Pictures Sham! Pictures! Spackler
Link Posted: 6/11/2003 4:23:14 PM EDT
Lots of good info here.
Link Posted: 7/17/2003 4:04:53 PM EDT
I was a bike mechanic for nearly 20 years before my present job. I too know about the calibrated arm! Its very common among people who things like this for a living to toss the ole TW and use the CA. If you look in a service manual you will sometimes find torque specs for srews. I have yet to see anyone use a torque screwdriver. I did this in my first build. I used my clicker TW and watched the notches just to see what happened. It clicked at 35lbs and then tada! There was the notch! Next time there will be no torque wrench.
Link Posted: 7/22/2003 8:24:28 PM EDT
Thanks everyone for this thread,especially Shamayim! I just barreled an upper with a FIRSH and it went perfect using your tips!
Link Posted: 7/22/2003 11:47:59 PM EDT
[Last Edit: 7/23/2003 12:11:26 AM EDT by TAC40]
The biggest issue to torquing something is to understand how and why you apply the torque. It can be as simple as to prevent you from damaging the part or keeping a joint from leaking to keeping the joint made up (tight). Torquing of the barrel nut has nothing to do with retaining the barrel in place. That function is done by the fact that the gas tube extends through the nut and acts as a lock pin. Yes the nut can rotate slightly, but it will not come loose and the barrel will not fall off. Since the barrel nut does not make up a gas tight seal, it is not torqued to prevent leakage. Therefore it must be torqued to maintain the designed accuracy, ie, preventing the rotation of the barrel during operation. This rotation is limited by the pin on the barrel extention, but accuracy is hugely affected by rotation. Now that we know why we torque the barrel nuts, lets discuss how. Below is a diagram and formula on how to properly use a torque wrench with the armorers tool attached. Many of you will find that the torque they have applied is greater that the designed specs because they used the torque wrench and armorers tool wrong. This formula is for calculating the torque applied if the armorers tool extends beyond the end of the torque wrench in a straight line, that is, making the wrench longer. M1 = M2 x L1 / L2 Where: M1 is the torque setting of the wrench. M2 is the actual torque applied to the nut L1 is the normal length of the wrench L2 is the extended length of the wrench [img]http://photos.ar15.com/WS_Content/ImageGallery/Attachments/DownloadAttach.asp?sAccountUnq=34121&iGalleryUnq=861&iImageUnq=15114[/img] When the wrench and extension are at 90° the actual torque is the same as the indicated torque
Link Posted: 7/25/2003 9:31:19 AM EDT
Depot level Armorer, seems to echo what many have said: [url]http://www.ar15.com/forums/topic.html?b=3&f=4&t=166070[/url]
Link Posted: 7/25/2003 10:04:55 PM EDT
Originally Posted By TAC40: The biggest issue to torquing something is to understand how and why you apply the torque. [...el snippo...] Therefore it must be torqued to maintain the designed accuracy, ie, preventing the rotation of the barrel during operation. This rotation is limited by the pin on the barrel extention, but accuracy is hugely affected by rotation. Now that we know why we torque the barrel nuts, lets discuss how.
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First of all, that's [b]not[/b] why you torque the barrel. In fact, cranking down really really really hard to keep the barrel from turning is a particularly bad idea from an engineering standpoint. I have no idea where you got this info, but I'd ask for my money back. In terms of accuracy the only purpose the upper receiver serves is as a rear sight mount to the barrel. There's no need to torque the rear sight mount to 30, 50, or 80 ft-lbs., just like on a flat-top upper there's no need to torque the carry handle thumbscrews. Hand tight works just fine. What stops the barrel from turning in the upper is the locating pin and slot. The pin should be tight in the slot with no side-to-side play. If there's room to move, you get rid of it by [b]gently[/b] peening down material on the side of the slot with the barrel in place using a hammer and punch. (Light taps!!!) Sometimes it's there already, and sometimes you opened it up in order to get the front sight straight. But either way you can easily tighten it up. After that you spin on the barrel nut, and you still don't need a torque wrench.
Link Posted: 7/26/2003 11:16:34 PM EDT
I just put my 24" Colt HB Elite barrel onto my A2 receiver this evening.Took about 2 minutes.Hand tightned the nut plus.It fell into place.The gas tube hole lined up really close.I used the gas tube to align the holes through the nut.The gas tube slipped into place on my front sight post.This wasn't so bad.no big deal until I realized the gass tube roll pin has gone missing.I had more trouble finding a solution to installing the spring in my A2 rear sight.The M16A2 AG helped clue me in.I made a dowel with a slot large enough to pass the roll pin through.Thanks for all the comments and suggestions.
Link Posted: 7/27/2003 2:55:43 AM EDT
I don't see what the problem here is. I'm not an aircraft mechanic or a nuclear related whatever and i've known how to properly use a torque wrench since i first started working on cars, CHRIST! Its no big deal! I've found that it is seldom much more effort to do things the "right" way (ie the way the manual says)and usually if it can't be done the right way there is some sort of problem that you might want to fix anyway.
Link Posted: 7/28/2003 7:31:57 AM EDT
I have to agree with the the majority here. Tighten your barrel nut hand tight and then tork to the next groove to allow your gas tube to slide through. NOTE: Don't forget to install your slip ring assembly BEFORE you install your barrel. Happy shooting! DG
Link Posted: 7/28/2003 12:45:51 PM EDT
[Last Edit: 7/28/2003 12:46:13 PM EDT by Paul]
Using a torque wrench is a "big production" [lolabove] What do you call changing the spark plugs on your car then? [lol] I've only build 6 of my uppers and changed out barrels on a couple of others, I use a torque wrench which isn't as big as a production as using a non-torque wrench as they sit under my work bench and the torque wrench sits on a shelf above. Bending over and unlocking the tool chest is such a "big production". I wouldn't have kittens if I couldn't build one the right way nor do I loose sleep because I'm so anal to actually follow the documentation. I do remove the tags from my bed mattress, change my oil every 3000-7000 miles or so when the weather isn't too bad, and actually shoot Wolf ammo in my rifles on occassion. Torque Nazis! [:D]
Link Posted: 7/28/2003 5:03:17 PM EDT
[Last Edit: 7/28/2003 5:15:20 PM EDT by imcoltsguy]
This subject has probably already been done to death, but I'd like to throw out a couple of opinions just the same. 1] If you ever want to remove the barrel from the upper receiver, DO NOT use Loctite. Not even the non-permanent kind. First, you don't need it. The gas tube will prevent the barrel nut from coming loose. Second, if you don't use some sort of lube on the threads during the assembly, you can forget about ever taking it apart again, especially after some use (note that lube and Loctite don't work together). 2] If you torque a barrel nut to 150 pounds, regardeless of what Colt said, you are definitely doing something wrong. And you will probably tear your workbench to pieces if you ever want to remove the barrel,not to mention straining a few muscles. 3] Shamayin, since you've been around long enough to know how to do it, I would trust you to put an upper together using only a C clamp, but I sure don't recommend lots of people doing so who don't have your experience. My action block is one of my most valuable tools, and with only the deepest respect for your methods, I'll keep on using it on the ones I build. Whether to torque or not...? I don't use a torque wrench, but I did while I was developing that "calibrated arm", so who is right? I don't know. I do know that until you know what you are doing, using a torque wrench isn't a bad idea. I also know that using a torque wrench can cause some people to use too much torque, not to mention inflicting lots of mental stress on themselves. Like most things, there's some value in both sides of the argument, in my humble opinion.
Link Posted: 7/29/2003 4:33:34 AM EDT
Thanks for all the great info on this thread, guys. I learned a lot reading it. I've not yet tackled an upper build, but I've recently started a new project that might required me to build exactly what I want. I was really worried about trying to install a barrel until reading this thread. Again, thanks for all the great info. I'm starting to think maybe I can build that upper after all.
Link Posted: 7/29/2003 5:28:11 AM EDT
Hey, guys. I have been following all this. I did complete the installation of my barrel. I agree that once hand tight the next alignment hole is what you want. That said, my barrel nut is ~90-95 ft-lbs, now don't say I have not been listenning to all your recommendations , I believe there are situations were you can't get it in the right range. My first hole is only barrely hand tight, I had to go to the next hole, 2 solutions were possible: 1- lap the receiver face 2- change the nut to get a different thread engagment. Having already torque it to 95 I decided to just leave it at that. Also, with the idea that the gas tube will retain the nut if it becomes loose would cause a problem with a free float tube, because the tube would become loose as a result of this, a delta ring would be less of a problem. But you are all right about the simplicity of changing barrels, I had been reluctant to attempt this kind of work. This experience opens a whole new dimension. Thanks for all you input.
Link Posted: 7/29/2003 3:01:06 PM EDT
Could we now kill this thread?? [beathorse]
Link Posted: 7/29/2003 4:26:35 PM EDT
Just a few days ago I finally got around to replacing my A1 upper on my main rifle with an A2 upper, and it took half an hour, start to finish, with the right barrel wrench, a torque wrench, a hammer, a small punch, and a receiver vise block. It lined up perfectly at 40 ft-lbs. Good enough! I have yet to see a barrel nut, barrel, and receiver that failed to align the notch by the time you hit 80 ft-lbs of torque, and if I did, I'd exchange the barrel nut for another one if it wasn't too difficult to remove the sight tower. Otherwise, I'd swap the receiver or the barrel assembly. Having installed a few barrels on receivers, I'd now say that the torque wrench isn't necessary if you have some conmmon sense and can guesstimate the amount of torque you're applying. You'll never need as much torque on a barrel nut as it takes to remove a properly installed lug nut on any car. CJ
Link Posted: 7/29/2003 7:57:22 PM EDT
OK guys! First off, the gas tube is not intended as a barrel nut lock.. If you torque the nut to 30+ FT. LBS. and the nut moves, you have some serious problems that extra torque won't even begin to address... Also, any lubrication, grease or oil, will affect your torque spec., and it has nothing to do with displacement.... I used to be anal about torque... and I have been around for awhile.. Hell, I've got shorts & socks that are older then most of you guys! But, I agree with the general consensus, that you can get a pretty good feel for tight with just a breaker bar, and some common sense! BTW, the tighten, loosen tighten, technique does work, it may be working on the threads a bit... but is isn't any more severe then removing and replacing a barrel... I change barrels out pretty quick...it's not an issue with me.... I still like to bring it up to tight with a torque wrench, just to know where I'm at... but I have no doubt, that many of the forum members are just as close, using the "by feel" method of tightening the barrel nut! Spin it on, lube it up, tighten it down, and forget it! Neat guns! till...later...GT
Link Posted: 7/31/2003 12:23:51 PM EDT
Originally Posted By GLT: OK guys! First off, the gas tube is not intended as a barrel nut lock..
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Several years ago at Knob Creek I had to completely assemble (including rebarrel) a Colt model 613 in my room at the Shepardsville Best Western. It was supposed to be finished already, but instead I was literally handed a paper Winn-Dixie bag full of loose parts. All I had to work with was my Swiss Army Knife and a rusty pair of slip-joint pliers that I had found in the parking lot that night. It was Wendesday night, and none of the dealers would really be set up until Friday to sell me tools, and I had to get this gun ready for sales demos the next day. Everything was going together pretty well, and then came the barrel. I stuck the upper receiver in a dresser drawer with the front sticking out, braced my back against the bed, and used my feet against the drawer front to wedge the upper in place. I wrapped a motel towel around the barrel nut and turned it as hard as I could by hand. Luckily a gas tube notch lined up pretty close, so I installed the tube and handguards and pronounced the project finished. The pliers made a dandy little hammer to pound the gas tube roll pin in. The next day at the range, all I had was a bunch of green, dented Paragon .223 ammo. I figured what the hell, and loaded up a magazine. The first round was so dented that it wouldn't even chamber, so I did what all FrankenAR WECSOGers would do and pounded on the forward assist several times as hard as I could until the bolt closed. It took about 6 or 8 good whacks, but I got it closed. (Who says FAs aren't useful? [:D]) I stepped up to the line, pushed the selector to Semi, aimed downrange and squeezed the trigger. BAM!!! Hey, it worked!! So I fired off a few more, and they went off without a hitch. Then I pushed the selector to Auto and emptied the magazine and the bolt locked back. I walked back to the benches, loaded up some more mags, and emptied them all with no malfunctions. Then I noticed someone had brought an old, beat up Colt 3x carry handle scope, so I popped it on the M16, took aim at the side of a railroad tie at the end of the range and fired. I was a couple feet low. I showed my buddy, and he said "What did you expect? That's 400 yards. What's the scope set to?" Oops! I didn't even look. I cranked the BDC from 100 to 400 and fired another round. BANG! ...whack!! Hey, I hit it! And again, and again, and again.... For the rest of the weekend I shot the crap out of that M16, a total of about 3,000 or 4,000 rounds over the course of 3 days. One of our customers tried it, and was so impressed that he later bought it. I didn't realize until after the transfer, so I called up the customer and offered to replace the barrel if he has any problems. He said thanks, but the rifle is working just fine. That was about 1990, and to this day that guy still owns and shoots that M16 with my hand tightened barrel nut. So GLT is right - the the gas tube is not [b]intended[/b] as a barrel nut lock, but apparently it doesn't work too bad as one either. [}:D]
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