Barrel nut torque(excessive),free float tubes, and more?

Hooked

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Allright here goes
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A few weeks ago I put together a DPMS Oracle from a kit.When it came time to torque the barrel nut, I applied some anti-sieze to the threads and a little to the face that contacts the barrel extension.I tightened and loosened to 30lbs a couple times and looked to see where the extension was in relation to the upper reciever (~.050"?).Now time to torque it and I figure I can get the alignment without being excessively tight...wrong. About the time when the nut failed 80 FtLbs, the gas tube aligned perfect.When I say failure I only mean one of the tabs (tooth?) broke, not the integrity of the nut itself (i don`t think).
So next I have to break out the file to make the four rail hand guard work (slightly bent tooth next to the broke one).
BTW- at this point I hope you`re laughing with me, not at me!
The next thing to go wrong is after about 120rnds the gas block come loose...before I realised this, I tightened down the hand guard thinking it was loose on the stamped plate. Now after tightening the gas block back up the stamped plate and hand guard still have movement slightly.
Probably have close to 200 rnds through this thing now and it does not meet my expectations, accuracy wise.
3.125" 20 rnd group at 100 yrds (about a minute max I think)
Best 5 rnd group is 1.5" at 100 yrds.
What do you all think..( hey! be nice! I know what you wanted to say..lol)seriously though, I think it should do better.
Will excessive torque degrade accuracy this much?
I want to get a free float tube now anyway, `cause I can`t handle that handguard flopping around like Lamars javelin.
Do free float tubes come with the nut when you buy them? do they use a standard wrench? Should I remove the barrel completely from the receiver before installing a new tube? Should I clean all the anti-sieze off and just use some loc-tite at much less torque?
At least the lower went together nicely.
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Both times I have installed barrels, they took 70-75 FtLbs
to line up correct.
I don't beleive Heavy torque is not going to hurt accuracy.
If you want good accuracy, your going to need a free float tube. Don't use Loc-Tight on the barrel nut, just use some good grease, I use Tetra grease.
FF Tubes come with a barrel nut.
 
I was waiting to see some of the experts reply to this, but here's my take on it.

ff tubes do come with the barrel nut. Most use a standard wrench, although I think the Hogue overmolded one is different, and probably some others. Mike Millie's ff tubes use a different system with a 2 piece barrel nut that eliminates the problem of torquing and lining up the gas tube holes. It's very nice to install and priced right too. I highly recommend. On the cheap route, the Model 1 ff tubes work well also and they're $35 at Midway.

Yes, I'd pull the barrel out, clean off the barrel extension, and even lap the face of the receiver before installing the new tube. I'd clean off the antisieze and just lube the threads a little, no loc-tite needed.

This is a pic of my lapping tool as it fits in the upper. Midway sells one just like it for $26 dollars I think. It may not help, but I had one upper very out of square and this made the difference between a mediocre shooter and a really accurate rifle.

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This is a pic of the squared upper. I use valve grinding compound to lap the receiver. It's a very quick and easy process. With just a few turns it will be apparrent if you've got any high spots that are causing the barrel to tighten down unsquare. It's hard to tell in the pic but there was way more taken off of one side than the other.


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Oh and believe me I'm not laughing at you or with you. Anyone who's done this stuff has been where you're at. HTH
Russ
 
Thanks for the input you guys, and encouragement 204 AR. I have had a few thoughts / ideas about making my own barrel nut and ff tube believe it or not...it would not eliminate the issue of the gas tube lining up, but reduce it anyway.
The lapping tool is a great idea, I will have to make one.
I almost stopped to `regroup`, at about 70ft lb, but was in a bit of a hurry or anxious to try it out, and only had one day off. (gotta have some kind of excuse!)
Thanks again, I really appreciate the input...I wonder now how perpendicular that face is to the bore...because of the gap I mentioned...maybe it was contacting at the bottom.
I will check out the different FF tubes mentioned.
I think I can also picture a design to eliminate the alignment issue alltogether too. Tighten the the nut with a hex or spanner on the O.D.
 
Originally Posted By: 204 ARHylander, I was typing as you responded, didn't mean to imply anything with my first line, lol.
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No worries, I'm definaly not an expert.
I like the idea of lapping the Receiver face, but don't like the idea of removing the Anodizing exposing the bare softer Aluminum. I may try it anyway.
 
204 what did that lapper cost you?
do you have to worry about headspacing after you lap? new to the ar game and want to know if i can get into it or not with my 204 upper without having to much problem.
 
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Originally Posted By: nastynatesfish204 what did that lapper cost you?
do you have to worry about headspacing after you lap? new to the ar game and want to know if i can get into it or not with my 204 upper without having to much problem.

Headspace is all in the bolt and bbl extension. Lapping the rcvr face will not have any impact on headspacing.
 
The lapping tool didn't cost me anything, a buddy turned it for me as a favor. We trade back and forth, etc. But the one like it on Midway is $21 something. It doesn't get very good reviews, though.

If I had a lathe, I would true the upper with it instead of lapping, but I don't so this is how I do it.

No worries about headspacing, that's all between the barrel extension, (which is already fitted to the barrel), and the bolt. This will simply cause the barrel to sit back in the receiver a tiny bit further than it would have otherwise.

Hylander, I thought about removing the annodizing as a problem also, but those worries were put to rest by one of our premier sponsors/builders here. When I posted on here about a problem upper last summer he suggested that an unsquare upper could cause the problems I was having. It turned out to be very unsquare, and truing it up solved the problems. IMO uppers should come squared up, while they're doing all the other machining you wouldn't think it would be too hard to do.
 
Quote:IMO uppers should come squared up, while they're doing all the other machining you wouldn't think it would be too hard to do.


They absolutely should. On a CNC machine, all that requires is a tool change and a clean-up pass across the face. It wouldn't take 15 seconds and every one would come out of the factory identical.

D-Tech does that to every upper he builds. If I had a tight barrel nut problem and accuracy issues like you're describing, it would be the first thing I'd check out.
 
I rough turned a couple of lapping tools today, and will finish them between centers on Monday if time allows.
Looking inside the receiver it appears there is a tiny bit of room for the barrel to move back, then it will be flush at the bottom.
Supposed to have tomorrow off, so I will dissassemble and investigate further.
Thanks again.
 
While I'm not certain that I would actually either use or recommend them, AR-15 Barrels.com does sell barrel nut indexing shims, as shown here: Barrel Nut Indexing Shims

I sure could have used some of those when I was wrenching on M16s for Uncle...
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Originally Posted By: Terry N.While I'm not certain that I would actually either use or recommend them, AR-15 Barrels.com does sell barrel nut indexing shims, as shown here: Barrel Nut Indexing Shims

I sure could have used some of those when I was wrenching on M16s for Uncle...
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I would like to order a few of these shims, but I can not find any contact info.
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Terry N. Welcome to Predator Masters
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Thanks for the link about the brrl. nut shims..I have been wanting to `jethro bodine cypher` and figure out how many degrees turn per .001" removed from the receiver,and that link has the math allready done.
 
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The lap revealed what I had suspected in regards to making contact at the bottom.
I found some adhesive backed 100 grit paper that worked good.
I will call Mike soon and get a ff tube ordered.
 
I hope that turns out to be the problem, and you're AR shoots better for you now. Keep up informed.

Russ
 
Ok, first the good news; installed the new free float handguard and it looks super. I had enough time to put 40 rnds of factory Remington 50g HP`s through it and it shoots much more consistant (2" groups at 100yrds).
The bad news...(big sigh), I put the barrel nut assembly a little to close to the receiver and now it does not pivot on the front pin like my other rifles. Dang! I even looked at one of my other rifles to compare before installing
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Hope to have time tomorrow evening to try some reloads in it and post a photo showing the new FF Tube from Mike at DTech.
Very nice product Mike
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This is how she looks now. Note how the swimming pool cover is blowing..not a good day for trying out some reloads.
Definately not hard to fix the barrel nut, but because I used some blue lock-tite, I`m going to wait `till I can borrow a heat gun and small strap wrench.
I can live with it the way it is now, I just need to be mindfull when separating the upper/lower. As it is though, the upper only swings over to like 2 o`clock (from straight up) before the brrl.nut hits the lower.
Why is it I seem to have to learn everything the "hard way"?
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ETA- PS..please don`t answer that
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