View Full Version : Barrel Nut Torque Question???
This is my second build and the barrel nut is less than cooperative this time. My first build the nut lined up with a torque of exactly 55 Ft/lb's but this time I am am not getting so lucky, I am in the high 60's probably close to 70 ft/lbs at best to get the scallop to line up properly.
I am using a standard barrel nut, Spikes upper and a daniels defense lightweight contour barrel. I read somewhere that Spikes make a shim kit, is this something I should be looking to get or just let it go with this torque? Like I said I am close to 70, I set the wrench to 65 as a max and had to push just a little little hair past the 65 torque to get the scallop to line up so I am guessing somewhere around 65-70.
This is my second build and the barrel nut is less than cooperative this time. My first build the nut lined up with a torque of exactly 55 Ft/lb's but this time I am am not getting so lucky, I am in the high 60's probably close to 70 ft/lbs at best to get the scallop to line up properly.
I am using a standard barrel nut, Spikes upper and a daniels defense lightweight contour barrel. I read somewhere that Spikes make a shim kit, is this something I should be looking to get or just let it go with this torque? Like I said I am close to 70, I set the wrench to 65 as a max and had to push just a little little hair past the 65 torque to get the scallop to line up so I am guessing somewhere around 65-70.
Are you using anti-seize compound on the threads?
If not, use it.
Then try the "3 times" torque technique and see if the next slot doesn't creep it's way closer to alignment without over-torque as the threads get happier together.
Are you using anti-seize compound on the threads?
If not, use it.
Then try the "3 times" torque technique and see if the next slot doesn't creep it's way closer to alignment without over-torque as the threads get happier together.
Ive tried that and am using a high temp choke tube grease. I was thinking about adding a shim and seeing if I can get it back to the the next tooth but considering that I was able to get the teeth aligned around 65-70 ish I would think I would have to add a few shims, don't really like that Idea either. Just a little concerned, I guess I just got really luck on the first build....
Ive tried that and am using a high temp choke tube grease. I was thinking about adding a shim and seeing if I can get it back to the the next tooth but considering that I was able to get the teeth aligned around 65-70 ish I would think I would have to add a few shims, don't really like that Idea either. Just a little concerned, I guess I just got really luck on the first build....
It happens. Easiest thing to do is to try a different barrel nut if you have more than one available.
It happens. Easiest thing to do is to try a different barrel nut if you have more than one available.
Thanks for the reply, I had two barrel nuts at the time of the build and ended up using the second one, the first was not even close to lining up. Actually taking it back part and using the first barrel nut may only require one shim. I am probably reading to deep into this but just don't want any issues later....
70lbs in within spec if it lines up. Stop over thinking it.
70lbs in within spec if it lines up. Stop over thinking it.
I am thinking your right, over thinking it. That is the engineer in me trying to stay in the mid range. I have heard of people even torquing slightly over 80 ft/lbs but am just being cautious...
The torque spec is so broad because the design will work with anything between 30 and 80 ft/lbs. and it is necessary to allow for alignment of the gas tube notch.
Berserkr556
07-28-13, 14:12
The correct grease is AeroShell 33MS and is what you should be using since it's cheap and readily available.
Quiet-Matt
07-28-13, 14:30
I have run into this issue before with a friends carbine. We went through 4 bbl nuts before we just worked one into position. We took our time and worked it tighten and loosen over and over. This basically just mated the surfaces with a slow polishing. No material was removed, just the park on the nut and bbl extension where the two meet was polished in the end. About every 5 times I would remove the nut and clean both surfaces. In the end it went together within the desired torque range and no damage was done. I kept the threads greased during the process.
is there any negative effect to accuracy if the nut torques up at the higher end of the range?..
is there any negative effect to accuracy if the nut torques up at the higher end of the range?..
That was my main cause for concern and of course detonating the upper because I torqued it to much....
Over torquing can cause deformation and failure of the threads. In this case, there's probably a little extra room to go over a little, but not something I'd want to put to the test.
Ideally, torque should be set to nominal; that is, the middle of the torque range. In this case, that is not only difficult to achieve but also isn't the goal. For the most part, keeping within the torque range shouldn't be difficult to do as that's how the parts are engineered to fit. Some over think it. They'll torque to the minimum (which if I recall right is 35 ft/lbs) but will continue without checking to see if everything lines up. Torque it to the minimum first, using the proper technique and check it. If it lines up, your'e done!
If the assembler cannot get the notch to line up between the minimum and maximum, the assembler should stop and re-evaluate the technique used. The barrel nut is system is engineered to line up within the torque range. Some don't realize they need to compensate for the extra arm of the barrel nut tool. When starting, they set the torque wrench to 35 but unless the arm is compensated for, they actual torque will be greater and the notch torqued past where it should be. Torquing to the next notch means they go too far and too much torque is needed. I think too that many assemblers don't reach a high enough torque during the first two tightenings and the parts don't set properly before the final torque.
Set the barrel nut tool 90 degrees to the torque wrench, set the wrench to the upper end of the torque range, torque and loosen two or three times. Then set the wrench to the minimum, torque and check alignment. If it's there, use it! If not, set the wrench to maximum torque and slowly tighten until either the next notch lines up or maximum torque is achieved. If it reaches max torque, loosen and start over. Torque again to the minimum setting and see how close it lines up. Maybe it real close and you just over tightened by a pound or two. Sometimes you just gotta know when it's good enough and accept it*
*What does "good enough" mean? It means it's within acceptable limits. If the notch lines up at the minimum torque it's good enough. If it lines up at the maximum, it's good enough. Both are within acceptable limits
Djstorm100
07-28-13, 20:36
Why set the barrel nut wrench 90 degrees to the tq wrench? If I under stand you correctly. The nut wrench and tq wrench should form a L
70lbs in within spec if it lines up. Stop over thinking it.
I agree.
jerhelo, everything sounds fine to me.
Joe Mamma
chasetopher
07-28-13, 20:54
Why set the barrel nut wrench 90 degrees to the tq wrench? If I under stand you correctly. The nut wrench and tq wrench should form a L
a^2+b^2=c^2 ... pythagor..... Former math teacher I digress...
Basically if you place it at a 90 you are much closer to the actual length of your lever(handle) in relation to the torque setting on the wrench, if you are adding a couple inches to the end of the wrench you are increasing that percentage to (for simplistic sake though there are several other factors to account for: ex add 2" standoff between barrel nut pivot point and torque wrench pivot point to a 10 inch wrench 2/10 = + 20% the torque setting; 70 ft lb becomes 84 ft/lb) hence the over torque.
As others have stated its such a broad range between 30-80 ft/lbs if it doesn't line up before you hit 80 chances are you're missing something.
Djstorm100
07-28-13, 21:43
I though that was it. This is why I use a crows foot when working on cars if socket will not work. I do wonder if they make a crows foot for a barrel nut if not easy to make one from a armorers wrench.
I though that was it. This is why I use a crows foot when working on cars if socket will not work. I do wonder if they make a crows foot for a barrel nut if not easy to make one from a armorers wrench.
I believe what he is saying in laymens terms, rotating the wrench 90 degrees changes the area or point of moment of torque where as keeping the wrench straight with the torque wrench you are increasing leverage increasing the moment of torque. I have heard this before I did my first build and did that this time as well.
Why set the barrel nut wrench 90 degrees to the tq wrench? If I under stand you correctly. The nut wrench and tq wrench should form a L
Because when the nut wrench and the torque wrench are at 90 degrees to each other, they form an L
Too much thinking happening here.
The TM specifies that the barrel-nut wrench should be inline with the torque wrench. The torque specifications in the TM are specified with the additional length of the lever already compensated for. With that being said, with a 50 lb-ft range for the target value, it's really not terribly critical as long it is tight enough to begin with and something isn't so terribly wrong that there is a risk of damaging the receiver.
I generally tighten to minimum, set my torque wrench to 80 lbs-ft, and as long as I get lineup without a click, things are good-to-go.
The TM specifies that the barrel-nut wrench should be inline with the torque wrench. The torque specifications in the TM are specified with the additional length of the lever already compensated for.
That is what I gathered from the instructions as well. The torque values listed are not at the nut.
Long story short, I had occasion once to simply file a new slot for the gas tube where the desired toque was indicated. A chainsaw file worked well for this. The gas tube should not bare on any portion of the barrel nut in the first place. The gas tube slots are simply for tool engagement, and loosing two slots at 12 o'clock will not hinder the proper use of most 3-pin wrenches by selecting/engaging three other opposing slots. The hole the gas tube passes through in the upper receiver provides all the alignment necessary.
Long story short, I had occasion once to simply file a new slot for the gas tube where the desired toque was indicated. A chainsaw file worked well for this. The gas tube should not bare on any portion of the barrel nut in the first place. The gas tube slots are simply for tool engagement, and loosing two slots at 12 o'clock will not hinder the proper use of most 3-pin wrenches by selecting/engaging three other opposing slots. The hole the gas tube passes through in the upper receiver provides all the alignment necessary.
Thats a pretty good idea but what I ended up doing was adding a spikes shim, changing to a different nut and got it to torque at exactly 70 ft/lbs on the money with perfect alignment, took about 5 times of loosening and re-torquing adding 5 ft/lbs but when it clicked at 70 it was exactly centered. This build was a little tricky...
Why set the barrel nut wrench 90 degrees to the tq wrench? If I under stand you correctly. The nut wrench and tq wrench should form a L
With the wrench offset 90 degrees, indicated torque = actual torque. It has to be 90 degrees though. Anything less (0-89 degrees) will require some math to calculate the difference between indicated and actual torque.
With the wrench offset 90 degrees, indicated torque = actual torque. It has to be 90 degrees though. Anything less (0-89 degrees) will require some math to calculate the difference between indicated and actual torque.
Actually there is a small sine error introduced with the wrench at 90*. Too small to worry about though...
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