Barrel nut torque
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You are currently reading a thread in /k/ - Weapons
I free floated the barrel on my ar and when I get home, will take it to the range for the first time.
Having not used a torque wrench, I just tightened it down really really hard.
It looks okay.
What are the chances there will be a catastrophic failure from micro cracks or some small bend or something?
The bolt moves freely, the gas block is probably in the right spot too.
>>29466414
Torque wrenches bear increments for a reason. Jesus Christ, are you abusive?
>>29466443
I don't feel abusive.
The factory nut was a real bitch to get off though.
I ordered an ar tool just to remove it and had to hit the tool repeatedly with a hamner, tried heat and eventually cut on it with a Dremel before putting all my weight on it to finally torque it off.
I'm a big guy.
I put a pmag in a vice between a couple boards and used that to hold everything. The soft would cracked but I think the pmag is okay... Haven't actually looked.
I think spec is like 30-80lbft which is a pretty big range so it should work... Most of the time you just have to take what the barrel nut will give you too line up the gas tube unless you want to fuck around with shims...
>>29466548
Okay thank you. Weird thing, has tube doesn't go through new nut so that isnt the problem, just wanted to make sure it was not going to work of because the hand guard is bolted to it.
>>29466662
The Daniel Defense barrel nut is like this. They recommend tightening to 50ft-lb
Could an over tightened barrel nut cause problems down the line or is it that if it works once it'll work forever?
>>29466414
You can get Craftsman torque wrenches on sale for $40. Everyone should have one, or three.
>>29466736
under-tightening can allow the barrel nut to loosen, and you rifle to fall apart.
over-tightening can damage your upper receiver and seriously gall the threads. Your rifle could fall apart the upper receiver fails.
>>29466769
But if it doesn't fall apart in the first 50 rounds it's fine?
Or is it a ticking time bomb?
>>29466778
That's a stupid question.
>>29466778
>But if it doesn't fall apart in the first 50 rounds it's fine?
>Or is it a ticking time bomb?
What could possibly make it suddenly stop working properly?
>>29467731
what is metal fatigue?
>>29467749
Are you saying the upper could kb?
>>29467827
yes, it's happened before where somebody had the upper threads separate from the main body after like 5k rounds
thread is on arfcom somewhere, I'm too lazy to find it, but the guy said he just tightened it up as much as possible
that being said you're probably fine, but I bought a torque wrench for 25 bucks off amazon because it was worth doing it right
>>29467884
Well shit....
Thanks for the information.
The spec for a regular non-FF barrel nut is like 35-80 foot pounds, which is a big range. When I did mine, I found that snugging it up to 35 pounds got it tight, then I kept going to the next available notch in the barrel nut for the gas tube. I ended up at about 65 pounds perfectly centered on the next available notch, which I was happy with.
The key is first to season the threads by tightening and loosening, otherwise you'll really fuck them up with too much torque. Grease also helps to decrease the friction that can gall the threads. Also, you want the last movement on the barrel nut to be tightening it to the tightest position it has yet been. For example, don't tighten it too far, then loosen it a couple degrees. You want to tighten, loosen, tighten, loosen, up until you're just below where you need to be. Then, as the final movement of the nut, tighten to the final destination and don't go too far. If you do this correctly you'll end up with a properly torqued barrel nut that won't loosen. If your last move is to loosen the nut slightly (i.e. you over torqued and need to back off some) then your nut will be prone to loosening itself from the vibrations of firing the rifle.
Mark the nut with paint against the receiver so you can keep an eye on it and know if it's moved.
You really don't need a torque wrench if you have a good feel for what you're doing, but it's nice to have a numeric value instead of "really really hard". Depending on how long the wrench you were using was, you're probably within spec, frankly. It would help to have some more details though.
Also, you should have used an upper receiver vise block or at least a makeshift vise block that directly attaches to the upper receiver. You said you torqued it with a pmag in a vise. Think about how long your chain of connections is to the barrel nut you're torquing. The vise holds the wood, holds the pmag, holds the lower, holds the pins, holds the upper. Too much room for flex.
>>29468016
cont.
Given how you had the upper secured, I highly doubt you over torqued the nut. If you had gotten to 80+ ft-lbs with that setup then there would have been all sorts of bending and cracking and popping that should have clued you that you need to stop.
Any time you're applying torque like that you want to secure whatever you're torquing as close to the application of torque as possible. The best way to accomplish this is to use a Geissele reaction rod, because you're applying torque against the barrel extension which is right underneath the barrel nut. If you're removing or attaching a muzzle device then the best setup is to clamp the barrel securely right behind the muzzle. With a wrench not all of the force you're applying is converted to torque. You're also pushing against whatever you're torquing, so if you clamp the upper receiver and tighten the muzzle device with a wrench, you'll be flexing the aluminum in the receiver as well.
The best compromise to a reaction rod is an upper receiver vise block, the best compromise to a vise block is two pieces of wood. Put the upper in horizontal and have the rail face against one of the pieces of wood and the bottom of the receiver against another piece of wood. Use wood that extends the entire length of the top rail and as far as you can go between the takedown pin lugs on the bottom, for the best distribution of force when you clamp it. This is a decent alternative and will allow you to torque the barrel nut without damaging the receiver.
Also torque wrenches can be had for $10 on sale at harbor freight. The Pittsburgh Steel brand ones. No excuses.
>>29468016
>>29468124
That was a lot to type out. Thank you for the good posts.
>>29468174
Pretty decent advice imo
>>29468223
Rather
>>29468016
>>29466414
>didn't torque it
it'll either be lose, or you'll break your upper eventually
>>29468016
>this whole tighten loosen thing
You realize there are literal millions of ARs out there that have never done this, right?
>>29469540
It's okay, not everyone has to build them perfectly. Obviously on an industrial scale some shortcuts are going to be taken.
There's plenty of ARs torqued to 100 ft-lbs with red loctite too.
>>29469540
and there are ARs out there that don't use 33ms ... but they're not my AR.
>>29468016
>Grease also helps to decrease the friction that can gall the threads.
That's not what galls threads you fucking idiot
It's steel on aluminum contact
>>29471009
First of all galling can happen between any two threaded metal surfaces, whether they're identical types of metal or not. It's more common with two different kinds of metals but it's still very possible with the same kinds.
Also you're acting like what I said was wrong and what you said is a correction of what I said. That's stupid. The fact that the receiver is aluminum and the barrel nut is steel definitely increases the chances of galling but the reason why the threads can gall is irrelevant. What I told him is all he needed to know, which I still stand by. The friction of the metals in the threads can cause galling, and adding grease as a lubricant, as well as tightening-loosening-tightening, will season the threads and help prevent galling.
Nothing about what I said was wrong and your an dummy.
>>29472738
>The fact that the receiver is aluminum and the barrel nut is steel definitely increases the chances of galling
>Also you're acting like what I said was wrong
If what you said about hardness of the two materials is anything to base off of, yeah, it is all wrong
The surface hardness of anodized aluminum is 65-70
Harder than most steels, and certainly harder than the barrel nut
And no, you don't need to "season" the threads
It adds no advantage and there is no disadvantage to not doing it
It's wasted time
>>29471009
In fact what you said is definitively wrong. Saying "steel on aluminum contact causes galling" implies that simply touching a piece of steel to a piece of aluminum will cause galling. Wrong. It's the FRICTION of the two that will cause them to gall.
This is why greasing and tightening-loosening helps. Obviously the grease slicks it up so that there's less friction. The tightening and loosening helps form the metals against each other so the threads aren't so coarse. It also makes the initial "break" in the tightening where you overcome the static friction less pronounced. That break is where you are most likely to gall the threads because that is where the friction is the highest. The surfaces of the threads are sticking to each other and want to pull apart. Seasoning and lubricating the threads prevents this.
>>29472814
Jesus man why don't you step outside for some air. Replying that fast to my reply of your post three hours ago. Have you been on 4chan for three hours anxiously awaiting my reply? Get some fresh air
>If what you said about hardness of the two materials is anything to base off of, yeah, it is all wrong
>
>The surface hardness of anodized aluminum is 65-70
>Harder than most steels, and certainly harder than the barrel nut
You're delirious, I said nothing about the hardness of the metals. Take a break buddy.
>And no, you don't need to "season" the threads
>It adds no advantage and there is no disadvantage to not doing it
Tell that to millions of mechanics. Working the threads before you reach the final destination prevents galling.
>>29472872
>You're delirious, I said nothing about the hardness of the metals. Take a break buddy.
hardness has everything to do with if a material will scratch (read: gall) another material
>>29472910
Uh, okay?
