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Posted: 3/25/2013 7:43:21 AM EDT
| I just completed a build using a Spikes billet upper and SS barrel. Heres my issue, in order to get the barrel nut to align properly for gas tube alignment, the torque is either under 20 ft lbs (too little ) or over 100 ft lbs for proper alignment of the gas tube. How much torque is too much? On my other builds it has always come in 30-50 lbs so I had no concerns . The gun shoots , but I'm having cycling problems, the bolt is not quite fully cycling ( some times will not eject) My thought is that the gas tube alignment is not quite right ( dragging on the bolt) I'm thinking I need to give it a bit more of a turn on the barrel nut , but I'm concerned I'm going to break something. Your wisdom and experiences would be appreciated. |
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I just completed a build using a Spikes billet upper and SS barrel. Heres my issue, in order to get the barrel nut to align properly for gas tube alignment, the torque is either under 20 ft lbs (too little ) or over 100 ft lbs for proper alignment of the gas tube. How much torque is too much? On my other builds it has always come in 30-50 lbs so I had no concerns . The gun shoots , but I'm having cycling problems, the bolt is not quite fully cycling ( some times will not eject) My thought is that the gas tube alignment is not quite right ( dragging on the bolt) I'm thinking I need to give it a bit more of a turn on the barrel nut , but I'm concerned I'm going to break something. Your wisdom and experiences would be appreciated. First, are you using the correct grease on the threads? 100 ft lbs is way too much… Did you do the correct procedure? Set your wrench to 30 ft lbs and tighten, back off the nut and retighten. Do that a total of 3 times. Then set your wrench to 80 ft lbs and tighten until the barrel nut is in correct alignment with the hole in the upper. If it still wont line up repeat the 1st step again, and retry. If it STILL can not line up you can either try a different barrel nut or use shims. |
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If you don't want to buy the facing tool you can lightly sand the receiver face. Obviously you don't want to remove very much. Most importantly don't remove so much that your feed ramps no longer line up. This would work. I use a perfectly flat piece of marble and and some 320 sandpaper for stuff like that. I would not remove any more then .015625 - .03125" if you go this route. |
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DO not removeTOO much. the amount is only about .001" to .0015". thousandths.
I use 400 to 600 grit. You only have to remove about .001" of anodizing to get it down to around 80 ft lbs. It is an extremely small amount that has to be removed. Generally not even all the way through the anodizing. A whole notch on the barrel nut is only .0027". It is easy to remove to much and be right back where you were if you are not careful. Thread is 1.25 x18 threads per inch. 1/18 is .05555" for a full turn of the barrel nut. There are 20 notches on the nut. .05555/20 is only .0027777" for a full notch of movement. You do not want a full notch. At .001" thousandths there will be over 1/3rd of a notch in movement. |
| OK so here is what I did to remedy the problem. I re torqued the barrel nut @ 30 ft lbs, I then marked the tab that was obstructing the gas tube pathway. I took a new chain saw file ( close to the diameter of the gas tube) and carefully filed the tab until the tube pathway was unobstructed. Re installed the gas tube, put the gun back together and test fired it in out back orchard. Works like a champ. Thanks for the suggestions people. I considered them all and took what was the most simple for me. Then I did it. |
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OK so here is what I did to remedy the problem. I re torqued the barrel nut @ 30 ft lbs, I then marked the tab that was obstructing the gas tube pathway. I took a new chain saw file ( close to the diameter of the gas tube) and carefully filed the tab until the tube pathway was unobstructed. Re installed the gas tube, put the gun back together and test fired it in out back orchard. Works like a champ. Thanks for the suggestions people. I considered them all and took what was the most simple for me. Then I did it. So not the correct way…. I would have gone more then 30 Ft lbs. What did you use for a lube? Did you tighten and back off a few times? |
| I actually wound up at 40 to get the free float tube to align too. I used some Tetra gun grease on the threads and tightened and re did a couple of times. The 30 ft lbs was a starting point ( minimum). This was a spikes billet receiver ($$$) I was dis inclined to dick with it. The barrel nut is cheaper to replace if I screw the pooch messing with it. |
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Did a barrel install this morning.....Moly EP on the threads, backed off at least 6 times...ended up at 92 ft lbs. I don't think this is "way too much" torque....would I be incorrect?
Even before my last adjustment at 92, when I loosened the nut it required little pressure and spun back easily, definately not galled. |
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Did a barrel install this morning.....Moly EP on the threads, backed off at least 6 times...ended up at 92 ft lbs. I don't think this is "way too much" torque....would I be incorrect? Even before my last adjustment at 92, when I loosened the nut it required little pressure and spun back easily, definately not galled. The max is 80 so I would say 92 is too much. The acceptable torque range is huge. If the barrel nut does not line up in that range then the correct thing to do is not make it tighter. Use shims, it will only take .001" or .002". Or try a different barrel nut. It is about stretching, not galling. I would think grinding down a tooth would better then either too loose or too tight, but even that isn't the right way to do it... |
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Did a barrel install this morning.....Moly EP on the threads, backed off at least 6 times...ended up at 92 ft lbs. I don't think this is "way too much" torque....would I be incorrect? Even before my last adjustment at 92, when I loosened the nut it required little pressure and spun back easily, definately not galled. The max is 80 so I would say 92 is too much. The acceptable torque range is huge. If the barrel nut does not line up in that range then the correct thing to do is not make it tighter. Use shims, it will only take .001" or .002". Or try a different barrel nut. It is about stretching, not galling. I would think grinding down a tooth would better then either too loose or too tight, but even that isn't the right way to do it... What is a source for the shims you refer to? I am assuming that these shims go between the barrel nut and the receiver? I did a search @ Brownells and came up empty. I am always looking for ways to do things better / more efficiently. On this build, I filed down the lug and it is totally concealed under the free float,so I am GTG for now, this issue may / will arise again |
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Barrel Nut Shims here:
Shims Shipping is expensive so you might want to buy the other things you need. |
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I just completed a build using a Spikes billet upper and SS barrel. Heres my issue, in order to get the barrel nut to align properly for gas tube alignment, the torque is either under 20 ft lbs (too little ) or over 100 ft lbs for proper alignment of the gas tube. How much torque is too much? On my other builds it has always come in 30-50 lbs so I had no concerns . The gun shoots , but I'm having cycling problems, the bolt is not quite fully cycling ( some times will not eject) My thought is that the gas tube alignment is not quite right ( dragging on the bolt) I'm thinking I need to give it a bit more of a turn on the barrel nut , but I'm concerned I'm going to break something. Your wisdom and experiences would be appreciated. First, are you using the correct grease on the threads? 100 ft lbs is way too much… Did you do the correct procedure? Set your wrench to 30 ft lbs and tighten, back off the nut and retighten. Do that a total of 3 times. Then set your wrench to 80 ft lbs and tighten until the barrel nut is in correct alignment with the hole in the upper. If it still wont line up repeat the 1st step again, and retry. If it STILL can not line up you can either try a different barrel nut or use shims. I'd tend to disagree. 100lbs is NOT way too much, in my opinion and experience. It is simply beyond the spec. It is totally normal to have some barrel nuts that line up perfectly at 20lbs (after torqueing three times), will almost always take more than 80lbs to get to the next gas tube hole. So what? You simply go to the next hole, no matter what. Shims, facing the receiver, swapping around barrel nuts, are certainly options... but there is no need for this. When this happens to me I simply torque it to 80 lbs about 10-20 times, then if it hasn't lined up yet during that process, it will be damned close and you just tighten until it lines up. People obsess about this torque stuff and it really isn't all that critical. |
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Did a barrel install this morning.....Moly EP on the threads, backed off at least 6 times...ended up at 92 ft lbs. I don't think this is "way too much" torque....would I be incorrect? Even before my last adjustment at 92, when I loosened the nut it required little pressure and spun back easily, definately not galled. It is absolutely fine. |
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Barrel Nut Shims here: Shims Shipping is expensive so you might want to buy the other things you need. Thanks |
Thanks people, I am now a wiser person
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I agree with FALARAK that it is a judgment call as to whether 100 ft-lb is "too much", but I think that needing to go that high indicates something is out of the ordinary with the fit between barrel, nut, and upper. I'm the kind of person who would keep poking until I found the reason instead of powering through despite something that was so clearly outside of expectations,
I also concur that altering a barrel nut to get the gas tube to fit is The Wrong Way to deal with the problem that poster presented. With all the millions of ARs out there, and with most going together smooth as silk within specs, going beyond specs would be an indication of something amiss, but grinding a tooth off of a barrel nut compounds the issue... It isn't my rifle, but that was absolutely not the way I would have done it. |
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Since we're on the topic... ....I don't own a torque wrench or have access to one...or a barrel nut wrench. Have a vise and some Vise Grips, though. You can get a torque wrench for under $20. Many armorer's tools run around $20 or so and have a barrel nut wrench on them. Use the right tools for the job. |
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what barrel did you use? im putting together my first upper aero upper dpms barrel nut Spikes Lothar Walther 18" Mid-length SS Fluted barrel torqued to 30lbs probably 10 time then to 70lbs 5 time still wouldn't line up it takes 90lbs to line up Interestingly I used the exact same barrel ( the SS walther 18") it was on a Spikes billet upper and allegedly a Spikes barrel nut. Take a look at the link , it is to Spikes who sell the mentioned shims. If I decide to take this one apart, that is the route I will take. http://www.spikestactical.com/new/z/rail-accessory-barrel-nut-shim-kit-p-605.html |
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Since we're on the topic... ....I don't own a torque wrench or have access to one...or a barrel nut wrench. Have a vise and some Vise Grips, though. Please do not even bring vise grips anywhere near to any gum. you will rue the day you do. If you are going to spend the money on gun parts, get the proper tools, they are not that much. |
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what barrel did you use? im putting together my first upper aero upper dpms barrel nut Spikes Lothar Walther 18" Mid-length SS Fluted barrel torqued to 30lbs probably 10 time then to 70lbs 5 time still wouldn't line up it takes 90lbs to line up Also be sure to use the appropriate grease. Using no grease will definitely give you an incorrect torque measurement. |
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Since we're on the topic... ....I don't own a torque wrench or have access to one...or a barrel nut wrench. Have a vise and some Vise Grips, though. Please do not even bring vise grips anywhere near to any gum. you will rue the day you do. If you are going to spend the money on gun parts, get the proper tools, they are not that much. Pretty sure he was kidding. |
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what barrel did you use? im putting together my first upper aero upper dpms barrel nut Spikes Lothar Walther 18" Mid-length SS Fluted barrel torqued to 30lbs probably 10 time then to 70lbs 5 time still wouldn't line up it takes 90lbs to line up Also be sure to use the appropriate grease. Using no grease will definitely give you an incorrect torque measurement. ^ This is very important |
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Since we're on the topic... ....I don't own a torque wrench or have access to one...or a barrel nut wrench. Have a vise and some Vise Grips, though. Please do not even bring vise grips anywhere near to any gum. you will rue the day you do. If you are going to spend the money on gun parts, get the proper tools, they are not that much. Pretty sure he was kidding. Sure hope so, I have seen alleged "gunsmiths " use some pretty inappropriate tools / techniques and really mar some guns, one of them was mine, I wanted to beat down the guy. |
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i used aero shell 33ms as far as i could tell that was the mil-spec grease ... It is indeed a MIL-G-21164D compliant grease, exactly the kind of grease called for in the TM. is (non-graphite)automotive bearing grease acceptable as well? yes |
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Since we're on the topic... ....I don't own a torque wrench or have access to one...or a barrel nut wrench. Have a vise and some Vise Grips, though. Nismo, try your local auto parts store. O'Rielly's out here in So. Cal. will rent tools for free. Maybe yours does. You can also try to find one at a local Pawn Shop; when I was a kid, my dad did some law work for a pawn shop, one time I went in there and the guy let me pick through all the tools and get what I wanted...pretty much got a whole socket set. Lastly, I just did a search at that big-online store that has a name of a river in South America; anyway you can get them from as little as $14. Please don't use Vise Grips. |
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