Float Tube Problem > Build It Yourself

Posted: 3/4/2005 4:14:25 PM EDT

Alright, big problem. I was changing the upper receiver on my RRA National Match A2 to an A4 and ran into trouble. I tried to unscrew the free float tube and the barrel nut came off with it. I cannot seperate the two pieces. I've tried PB Blaster penetrating oil, heat, brute force, etc. and it will not come apart. Pics are below. Any suggestions you may have for seperating the two pieces would be greatly appreciated. Thanks. MJD

Posted: 3/4/2005 4:17:15 PM EDT

[#1]

Umm...that thing that looks like a pin into the barrel nut, is that a pin?

Posted: 3/4/2005 4:18:44 PM EDT

[#2]

I do believe that the match FF tubes, like you have there are essentiall one piece. They don't come apart. I have on at home and it's the same way.

If you need a barrel nut, IM me.

Posted: 3/4/2005 4:22:39 PM EDT

[#3]

That is not a standard barrel nut by the way.

It's made for a FF tube.

Posted: 3/4/2005 4:27:31 PM EDT

[#4]

Quoted:
Umm...that thing that looks like a pin into the barrel nut, is that a pin?

No, it's not a pin, it's a hole. MJD

Posted: 3/4/2005 4:29:59 PM EDT

[#5]

The problem is, when I put the tube back on as it is (1 piece), it doesn't line up properly, it's about 90-100 degrees from where it should be and is very tight. I don't think I can get it around the rest of the way if I keep tightening it. MJD

Posted: 3/4/2005 4:30:19 PM EDT

[#6]

I have doen these tubes often and you are not supposed to remove the barrel nut for any reason and it is intended to stay on the free float tube.

Do not force it or it will be unservicable.

Posted: 3/4/2005 4:34:41 PM EDT

[#7]

Was it just on your upper hand tight when you took it off?

90 degrees at even 5 foot pounds seems like a long way to go.

Have you tried just hand tight and then see where you need to go from there?

Posted: 3/4/2005 4:35:47 PM EDT

[#8]

Spec calls for 35-90 Ft. lbs but you can get by just fine with less.

Posted: 3/4/2005 4:42:55 PM EDT

[#9]

Well, it's definitely 1 piece, I'm glad I didn't mess up a $100 tube. Let me try it by hand again and see what it does, be back in a minute. MJD

Posted: 3/4/2005 4:55:27 PM EDT

[#10]

Okay, when I get it lined up properly there is NO resistance whatsoever, I can still turn it freely. Please advise. MJD

Posted: 3/4/2005 5:00:27 PM EDT

[#11]

And another 360 is out of the question?

Posted: 3/4/2005 5:03:36 PM EDT

[#12]

Probably. Approximately 90 degrees after, the tube is hand tight, so I'd have to go another 270 degrees. My original estimate was obviously not right. It was on tight before, it was a bitch to remove. Think I should go the rest of the way? MJD

Posted: 3/4/2005 5:10:34 PM EDT

[#13]

Is this a new upper or the same one?

Posted: 3/4/2005 5:12:03 PM EDT

[#14]

It's a new upper, CMT A4 style. MJD

Posted: 3/4/2005 5:19:56 PM EDT

[#15]

Get some 250 grit emory paper and on a flat surface hold the upper good and straight, breach end down and just gently slide it around. Be sure to wet it first and keep it wet. Once you get to within 30-40 degrees hand tight "gitter done".

Posted: 3/4/2005 5:23:55 PM EDT

[#16]

Let me make sure I understand, The idea is to remove a little bit of metal so the barrel will move back a tiny bit and the barrel nut will go further without getting so tight? MJD

Posted: 3/4/2005 5:34:03 PM EDT

[#17]

Wont sanding down the face of the upper affect headspace?

Posted: 3/4/2005 5:38:05 PM EDT

[#18]

Yes.

Actually all you need is a couple hundreths of an inch.

I think it's like 18 tpi thread. (18 threads per inch).

That's 6480 degrees per inch. (360 degrees per thread, times 18 threads per inch).

Posted: 3/4/2005 5:41:11 PM EDT

[#19]

Quoted:
Wont sanding down the face of the upper affect headspace?

No.

Head space is set by the installation of the barrel extension on the barrel.

Another option might be to go and find some one that has 2, 3, 5 different uppers and see if one indexes better.

Posted: 3/4/2005 6:43:47 PM EDT

[#20]

There is nothing wrong with your float tube! In the second photo, the "hole" is actually in a lock ring and must be loosened to release the float tube from the barrel nut. First, secure the float tube in a vise being careful not to crush the tube. Just tight enough to hold the entire assembly without turning. Use your AR-15 all purpose tool and unscrew the ring a few turns to "unlock" the float tube from the barrel nut. You should be able to unscrew the barrel nut at this point.

Posted: 3/4/2005 6:50:54 PM EDT

[#21]

Rock River just uses a high temp loctite of course it's designed to come apart. you just are not using enough heat. Use a mapp gas torch and it will come of by finger pressure once the loctite burns off. I would take it apart for $10 and postage back to you if you can not get it apart.

Posted: 3/4/2005 6:52:34 PM EDT

[#22]

That makes sence.

Posted: 3/4/2005 7:27:59 PM EDT

[#23]

+ 1 thats a 3 piece RRA DCM tube and you took it apart wrong.

Probably the easiest way to get it apart now is to reinstall the barrel& tube on the receiver as to use it as a fixture. Use a torch as recommended to loosen the loc-tite on lock ring and back it off, than heat up the threaded portion of tube and unscrew the tube ( with strap wrench if necessary ) from the barrel nut .

Posted: 3/6/2005 7:47:48 AM EDT

[#24]

Good news! I got the thing apart! I used a propane torch to get it up to the temperature and it came apart pretty easy, with the exception of a second degree burn because I accidently touched the barrel nut while hot. Once apart I burned off the residual loctite and reassembled it properly. The whole assembly is rock solid now, it even took the play out of the handguards. I'm going to test it out in a few hours. Thanks for all the help everybody! MJD

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