AR-15 Castle nut tightening

[jsb889]

Okay. So I'm in a bit of a predicament.

I got my first AR built, and have about 100 rounds down the tube. I've had it to the range twice and it functions fine. However, the accuracy seems to be a little funny.

It'll shoot a half inch group at 100 yards, but it'll have fliers off by four inches. I'm not the best shot, but I can hold the most of the shots to nice tight groups and how far its off, its definitely not me.

I figured it was most likely because of how I had put on the barrel and castle nut, if you can call it a castle nut. Its the Custom Clark tube so its not quite a castle nut and you cannot use a castle nut wrench on it. Anyway, I get it hand tight and the holes line up perfect. If I try to tighten to the next hole...it get stuck in between holes. In other words, I can't tighten it up enough to get the next tightest hole. I literally broke a table trying to get it tightened.

Used a vice on the upper receiver and a wrench on the tube, with duct tape around it to prevent damage. I absolutely can't get it any tighter. I don't believe a block to put in the vice would help. I gave enough torque to break the table the vice was on. So, I'm hoping someone here will have some input on how to fix the issue, or maybe what the issue may be.

[JayBell]

is this a 2 piece tube?

if so, you put the upper in the upper block, then use the barrel nut wrench with the pins in the nut holes.

I use moly lube when assembling barrel nuts and tubes, and tighten, loosen, tighten, loosen until the proper hole in the barrel nut lines up with the gas tube hole in the upper.

thats how ya do it, you probably dont have the nut tight enough overall, but if it was loose, you'd have other more noticeable issues.

heres a quick video

[bac0nfat]

Do what I did and tighten it as tight as you can, then stake it, then realize that your buffer tube was crooked the whole time. NOT

[jsb889]

The barrel nut wrench won't work with the custom clark as far as I can tell. Its a two piece, and the nut part of it won't allow a wrench in there.

I tightened and untightened a ton of times, and it always ended up in the same exact spot and not able to tighten anymore, with the holes being equal distance if it tightened it or loosened it. Even after I added oil onto the threads, same exact spot. So, I need a good bit more of a turn to get the next hole to line up and I sure can't think of a way to do it.

I have no other noticeable issues. I did notice the nut has some carbon build up on it, I'm figuring that would be there regardless if it was tighter or not though. Like I said, she functions fine.

I think if I can't get this next hole lined up, I'll slap the scope back on and see if I can get some more info next outing. I put the gas tube on it and tightened her down as of now. If she gets awesome groups at first, thats most likely the culprit and I'll look into some loctite on the threads.

Maybe its something else, but I'm doubtful.

[51158]

I'm just throwing this out there. I don't have a clue as to how this nut captures the barrel.with that said.

Can you shorten the castle nut where it meets the barrel? ya know take nut in hand and place file on table and file the surface that meets the barrel

what do ya think?
should've watched the video first..

if you have the same setup as the video, It looks like that can take a shim between nut and barrel..that will move the hole in the tight position..

Like I said, I bought a complete upper when I did mine. next one will be a complete build.

[JayBell]

I'm just throwing this out there. I don't have a clue as to how this nut captures the barrel.with that said.

Can you shorten the castle nut where it meets the barrel? ya know take nut in hand and place file on table and file the surface that meets the barrel

what do ya think?
should've watched the video first..

if you have the same setup as the video, It looks like that can take a shim between nut and barrel..that will move the hole in the tight position..

Like I said, I bought a complete upper when I did mine. next one will be a complete build.

use of moly grease and tighten-loosen-tighten with a proper barrel wrench allows you to index the gas tube hole correctly.

barrel wrenches with the 3 pins are what is generally used on the barrel nut, not a strap wrench of any kind.

I have both the US mil wrench used with a breaker bar, AND the one piece with the 3 pins, and the other side with multiple fitted area for the standard handguard nut.

both with the 3 pins work on every 2 piece free float nut I've ever tried.

you just need the proper tool for the job here

[mike333]

I tighten mine up pretty damn tight and then stake the castle nut. Believe it or not, I've had a staked nut come loose before.

[tonyfac]

I tighten mine up pretty damn tight and then stake the castle nut. Believe it or not, I've had a staked nut come loose before.

how does this happen? once the barrel nut is torqued down, the gas tube goes through. how can it loosen without snapping the gas tube? i personally have never had one come loose, i am not saying it does not happen, but i have never seen it.

[ar15jules]

We seem to have a discussion about barrel nuts and buffer tube castle nuts going on at the same time. Ironically enough, I just did work on a rifle where the barrel nut loosened enough with the gas tube in place to cause major problems. I have no clue what it was torqued to before it came to me.
Jules

[Asmodeus6]

use of moly grease and tighten-loosen-tighten with a proper barrel wrench allows you to index the gas tube hole correctly.

barrel wrenches with the 3 pins are what is generally used on the barrel nut, not a strap wrench of any kind.

I have both the US mil wrench used with a breaker bar, AND the one piece with the 3 pins, and the other side with multiple fitted area for the standard handguard nut.

both with the 3 pins work on every 2 piece free float nut I've ever tried.

you just need the proper tool for the job here

This has now been posted twice and should solve the issues you are having if those are indeed your issues.

Oil, grease, and other thread lubricants are not = to moly lube. There is a reason it is the standard for serious automotive fastener companies, and often supplied with the fasteners. You will naturally bed the threads tightening and loosening the nut which will allow you to get where you need to be. Use a torque wrench. There is a minimum and a maximum. So get it up to the minimum torque specifications and line up the first hole. If you can't get this done, then leave it to someone who can. Bedding the barrel to the upper receiver with loctite is done by some, but they also true the receiver threads to the barrel extension and other small things. But that isn't the threads, it's the receiver socket. Many have said however... the heat generated by firing the weapon would destroy any kind of bond created by doing this anyway. And it will just make pulling the barrel in the future a huge PITA.

2. Barrel nut - fastens the barrel to the receiver.

3. Castle nut - holds the receiver extension (aka- buffer tube) to the rear of the receiver.