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Posted: 6/5/2014 7:23:43 PM EDT
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Hi this is Mark from Tupelo MS, this is my first post, but been lurkin ar15 for years now... :)
I would greatly appreciate any input on my build in progress... Anyway, I just bought an upper receiver online and I noticed that my barrel nut is wobbling when I tried it on my receiver. is this just ok or there should be no significant wobble at all? I think the wobble will disappear when I install the barrel but iI feel like there should be no wobble at all even wothout e barrel.  . I believe its the receiver that has a smaller thread pitch as I've tried it on mu buddys receiver and theres hardly any wobble... Also tried using his mil spec barrel nut and also has wobble on my receiver. Is this something I need to be worried about?
unfortunately my barrel haven't arrived yet Below is the video clip of the wobble...please enlighten me! Thanks! http://youtu.be/E6GfxFrFZNQ |
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I'm guessing you've never done machine work before, but nut wobble is completely normal. When you torque it down, it will take the play out of that. Normal (tolerance stacking is normal, but OK so long as the threads catch and hold). Put your barrel in, torque it down, and the nut will lock into the threads. No more wobble. Perfectly A-ok.
ETA: yes, the threading on your upper is on the lower side of "spec", but appears to catch the nut threads just fine. IMHO, I'd still use that without any hesitation. |
| I would be concerned about having that much play. Of course it would tighten down with the barrel installed, but I would be concerned about it not applying even pressure all the way around the barrel nut with that much play. Not to mention if the threads aren't seated deep enough in the grooves it could even strip the threads of the receiver when you try to torque it down. |
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Nice choice on the rail... while you have the parts, did you see if the geissele rail fits the upper? The anti rotation tabs may not fit with a billet upper.
But that doesnt seem right, I cannot say 100% that something is wrong because I never tried putting a barrel nut on without a barrel |
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Quoted:
I'm guessing you've never done machine work before, but nut wobble is completely normal. When you torque it down, it will take the play out of that. Normal (tolerance stacking is normal, but OK so long as the threads catch and hold). Put your barrel in, torque it down, and the nut will lock into the threads. No more wobble. Perfectly A-ok. ETA: yes, the threading on your upper is on the lower side of "spec", but appears to catch the nut threads just fine. IMHO, I'd still use that without any hesitation. Ill second this. |
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I'm guessing you've never done machine work before, but nut wobble is completely normal. When you torque it down, it will take the play out of that. Normal (tolerance stacking is normal, but OK so long as the threads catch and hold). Put your barrel in, torque it down, and the nut will lock into the threads. No more wobble. Perfectly A-ok. ETA: yes, the threading on your upper is on the lower side of "spec", but appears to catch the nut threads just fine. IMHO, I'd still use that without any hesitation. I'm not a master machinist but I used to own a mini lathe for a hobby :) anyway I think ithe wobble will be gone when i torque it down with the barrel, but at the back of my mind I'm thinkin when It all heats after maybe 100 rounds the catch of the thread might soften and I'd be pickin my barrel downrange :) My 2nd issue is I bought an Adams Arms xlp , and I start sizing things up, it won't fit in my barrel nut and rail, but I won't give it up as the thought of this build started when I saw AA...anyway I'll deal with it later. Heres what I got so far.. North Tech defense barrel is incoming http://i57.tinypic.com/9rm8i9.jpg http://i57.tinypic.com/b3tvg7.jpg |
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It has anti rotation tab, but worried more on it going forward when the thread heats up and soften ..... It might get a little catastrophic :) That billet upper looks like it wasn't cheap. For the price you most likely paid, it should be perfect. I would call them up. |
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When you first started I thought much ado about nothing, but by the time you got it screwed on all the way I had changed my mind. If me, I would use a torque wrench and torque it to either 80 ft-lbs or the max ft-lbs the barrel nut maker specs. If it holds ( with barrel installed of course) then I would back it off and to around 40-70 pounds to line things up and call it a day. But if the upper stripped the threads at max spec ft-lbs, I'd be wanting a new upper. Your video clip would remove any question about you causing the problem.
Unless that upper is made out of wax it is not going to ever get hot enough to 'soften' the metal no matter how hard you shoot it. That concern is completely unfounded. |
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Nice choice on the rail... while you have the parts, did you see if the geissele rail fits the upper? The anti rotation tabs may not fit with a billet upper. But that doesnt seem right, I cannot say 100% that something is wrong because I never tried putting a barrel nut on without a barrel It has anti rotation tab, but worried more on it going forward when the thread heats up and soften ..... It might get a little catastrophic :) |
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That is not normal, but probably not that big of a deal. With the barrel installed and tightened the wobble will be gone. I would measure the receiver threads diameter, and my barrel nut's inner diameter just to reassure myself how much thread engagement I had. It will not "soften" enough to send the barrel down range unless the threads are barely catching by a c***hair. (technical term) |
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That certainly does not look right.
You would be getting immediate cook offs long before you have a thread problem from heat. If it is a loose as it looks my SWAG is the nut could come loose while firing. Putting the calipers on the threads does seem like an obvious step. |
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OP: you got a few people telling you to measure the threads on the receiver. I gave you the dimension (1.25") and the tolerance is about .004". If you install your barrel, and the threads on the receiver strip, then what? Are you gonna show your video to the upper manufacturer (or reseller)? They will say you knew there was a problem and ignored it. You now have an expensive piece of scrap metal.
But who am I to offer advice? I am just another invisible poster on an internet forum. 
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Thanks for all the input guys...somehow a little relief for me... But yup I will make measurement to see how much thread is catching. Also one of the reason it bothers me is my previous AR does not have that significant barrel nut looseness...i could say almost no wobble at all... Keep 'em coming... |
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OP: you got a few people telling you to measure the threads on the receiver. I gave you the dimension (1.25") and the tolerance is about .004". If you install your barrel, and the threads on the receiver strip, then what? Are you gonna show your video to the upper manufacturer (or reseller)? They will say you knew there was a problem and ignored it. You now have an expensive piece of scrap metal. But who am I to offer advice? I am just another invisible poster on an internet forum. You're right man..... Will make measurement and check tolerance... 'Appreciate your concern ... But i knew you guys understand me , this is just the thrill of the build that affecting me. :) |
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I watched the video the OP put up. I would not assemble that as is I have never had a upper receiver and barrel nut with that much play, I would be a little concerned with that much tolerance stacking, It is fairly likely that once the barrel is Installed and torqued to spec. it may suffer from poor accuracy due to sloppy fit and/or barrel canting, etc. It may also cause head-space Issues and or function Issues, provided of course if other areas of the upper receiver/barrel nut are/or may be also out of spec... For me personally I would find that type of sloppy fit/poor spec./build quality unacceptable, even more so when have such a nice (and expensive) billet upper and FF rail... I have build quite a few AR-15's & LR-308/SR-25 type rifles from scratch and I have a background in Engineering/Machine Tool Technology, so I may know a few things about this subject, well anyway... Good Luck. |
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I have never had a upper receiver and barrel nut with that much play, I would be a little concerned with that much tolerance stacking, It is fairly likely that once the barrel is Installed and torqued to spec. it may suffer from poor accuracy due to sloppy fit and/or barrel canting, etc. It may also cause head-space Issues and or function Issues, provided of course if other areas of the upper receiver/barrel nut are/or may be also out of spec... For me personally I would find that type of sloppy fit/poor spec./build quality unacceptable, even more so when have such a nice (and expensive) billet upper and FF rail... I have build quite a few AR-15's & LR-308/SR-25 type rifles from scratch and I have a background in Engineering/Machine Tool Technology, so I may know a few things about this subject, well anyway... Good Luck. Quoted:
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I watched the video the OP put up. I would not assemble that as is I have never had a upper receiver and barrel nut with that much play, I would be a little concerned with that much tolerance stacking, It is fairly likely that once the barrel is Installed and torqued to spec. it may suffer from poor accuracy due to sloppy fit and/or barrel canting, etc. It may also cause head-space Issues and or function Issues, provided of course if other areas of the upper receiver/barrel nut are/or may be also out of spec... For me personally I would find that type of sloppy fit/poor spec./build quality unacceptable, even more so when have such a nice (and expensive) billet upper and FF rail... I have build quite a few AR-15's & LR-308/SR-25 type rifles from scratch and I have a background in Engineering/Machine Tool Technology, so I may know a few things about this subject, well anyway... Good Luck. I agree with you 100 %. I have been in the metals fab business for close to 45 years, including a few years in R & D, as well as running the engineering dept of a large company. Never would I accept that kind of fit in an assembly for my employer, even if it meant rejecting a few thousand pieces. And for my own stuff? No way in hell. 
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I agree with you 100 %. I have been in the metals fab business for close to 45 years, including a few years in R & D, as well as running the engineering dept of a large company. Never would I accept that kind of fit in an assembly for my employer, even if it meant rejecting a few thousand pieces. And for my own stuff? No way in hell. Quoted:
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I watched the video the OP put up. I would not assemble that as is I have never had a upper receiver and barrel nut with that much play, I would be a little concerned with that much tolerance stacking, It is fairly likely that once the barrel is Installed and torqued to spec. it may suffer from poor accuracy due to sloppy fit and/or barrel canting, etc. It may also cause head-space Issues and or function Issues, provided of course if other areas of the upper receiver/barrel nut are/or may be also out of spec... For me personally I would find that type of sloppy fit/poor spec./build quality unacceptable, even more so when have such a nice (and expensive) billet upper and FF rail... I have build quite a few AR-15's & LR-308/SR-25 type rifles from scratch and I have a background in Engineering/Machine Tool Technology, so I may know a few things about this subject, well anyway... Good Luck. I agree with you 100 %. I have been in the metals fab business for close to 45 years, including a few years in R & D, as well as running the engineering dept of a large company. Never would I accept that kind of fit in an assembly for my employer, even if it meant rejecting a few thousand pieces. And for my own stuff? No way in hell. You would think It's not all that hard to get a 5 axis CNC machine to control tolerances to within at least .003"-.005" in all critical area's...Really good shops will also have nice quality optical scanners in their QC department to avoid problems of this type...It's not like you have a $40/$50 upper and a $60 FF tube, even then... Your buying/building a product (an expensive one at that) that needs to be capable to withstanding pressures of 62,000 PSI + safely, I wonder how much consider- ation was made of this and the safety aspect if somethings goes really bad, just saying... All of this may be just some hot water, and it may work just fine with no problems at all once the barrel gets torqued to the receiver...but I can't help to feel a bit nervous considering the type of Instrument you are dealing with and the chance (even though a small one) that the operator and/or bystanders may get hurt (at worst) or you may damage your expensive rifle... Again, Good Luck. |
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I agree with you 100 %. I have been in the metals fab business for close to 45 years, including a few years in R & D, as well as running the engineering dept of a large company. Never would I accept that kind of fit in an assembly for my employer, even if it meant rejecting a few thousand pieces. And for my own stuff? No way in hell. Quoted:
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I watched the video the OP put up. I would not assemble that as is I have never had a upper receiver and barrel nut with that much play, I would be a little concerned with that much tolerance stacking, It is fairly likely that once the barrel is Installed and torqued to spec. it may suffer from poor accuracy due to sloppy fit and/or barrel canting, etc. It may also cause head-space Issues and or function Issues, provided of course if other areas of the upper receiver/barrel nut are/or may be also out of spec... For me personally I would find that type of sloppy fit/poor spec./build quality unacceptable, even more so when have such a nice (and expensive) billet upper and FF rail... I have build quite a few AR-15's & LR-308/SR-25 type rifles from scratch and I have a background in Engineering/Machine Tool Technology, so I may know a few things about this subject, well anyway... Good Luck. I agree with you 100 %. I have been in the metals fab business for close to 45 years, including a few years in R & D, as well as running the engineering dept of a large company. Never would I accept that kind of fit in an assembly for my employer, even if it meant rejecting a few thousand pieces. And for my own stuff? No way in hell. Count me in agreement......that is way too much slop and when torqued will place unnecessary stress on the top of the thread profile......no way something like that would make it out of my shop......and the actual diameter may or may not be 1.250.....most likely it'll be (and should be less) depending on how it was machined....when we cut a thread on the CNC lathe.....the deburring pass will reduce the actual OD.....where you want to measure is in the middle of the thread with a set of thread wires or the minor diameter with an Optical comparitor.................if you are near Macon GA and want to use mine....drop by the shop. |
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I just got off the phone with Lanworld's chief, as always they stand behind their product and will work with me on my concern.
They offered me many favorable options from total replacement or trying to make it work within the limits of safety. For now , i'm gonna wait it out until my barrel arrives and decides what I'm gonna do later. Great after sales service! Thanks for all who've chipped in to educate me. Will keep you posted on my build! |
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I'm guessing you've never done machine work before, but nut wobble is completely normal. When you torque it down, it will take the play out of that. Normal (tolerance stacking is normal, but OK so long as the threads catch and hold). Put your barrel in, torque it down, and the nut will lock into the threads. No more wobble. Perfectly A-ok. ETA: yes, the threading on your upper is on the lower side of "spec", but appears to catch the nut threads just fine. IMHO, I'd still use that without any hesitation. I have been in the garage all night, putting a few together, etc for tomorrow. Out of curiosity after reading this thread, I chucked up two barrels in uppers for my SBRs I am putting together; a 12.5 Crusader in a Noveske upper...no wobble in the NSR nut, and a Colt barrel into a Aero upper with the Colt mil spec nut, very slight if any wobble. I am not digging what he has going on in that video. I am not a machinist, but was a diesel engine tech for years, so I have experience with all types of threaded fasteners. It would be interesting to see the OD of those threads. I have a MK5 Gieselle inbound, I will try that one on my BCM upper |
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I am not digging what he has going on in that video. I am not a machinist, but was a diesel engine tech for years, so I have experience with all types of threaded fasteners. It would be interesting to see the OD of those threads. Me either. I wouldn't use that upper. A slight wobble would be fine but the video shows 2 completely different sizes barely working together with WAY too much slop. That's not tolerance stacking, just bad machining of the upper. I'd return it and get a new one that works or find another upper. |
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I player around with a YHM and a Spikes upper last night.
I used a YHM and a USGI barrel nut on both uppers. There is some play, but yours looks worse. The OD on the Spikes was 1.243”. However as was pointed out earlier what actually matters most is the amount of thread engagement. Most people are not set up to make that determination. |
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However as was pointed out earlier what actually matters most is the amount of thread engagement. Most people are not set up to make that determination. Did you see the video? With that much wobble, there isn't enough thread engagement to torque the nut anywhere near 80 ft/lb w/o risk of stripping. Very slight wobble would be ok but in the video, that's extreme. I just installed a SLR handguard and the aluminum barrel nut easily threaded onto a Cerro forged upper with almost no wobble at all. |
DX the upper.......I AM a machinist.....got my first lathe when I was 13 and have been cutting threads for over 40 years.....THAT (the video) ain't even close to being right.......the barrel nut threads have nothing to do with headspace......but as far as retaining the barrel....it just ain't right. While 80 pounds is the MAXIMUM torque to be applied to a GI barrel nut.......I would be concerned about deforming/damaging the threads on the upper at half that. Let the MFG replace it.....or make a custom barrel nut threaded to fit the upper. 
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