I bought a Colt 20" A2 upper at a gun show some time ago. It appeared brand new in/out. I've put about 1000 rds through it. Tonight as I was cleaning it, I thought the front sight was loose. Then I realized the whole barrel will move about 1/16" back and forth, independent of the upper receiver. It don't seem quite right. I assume I will need an armorer's block and barrel wrench before I can do anything about it.  Anyone ever had this before, or know what's wrong? My RRA 16" (unfired, got it today) doesn't wobble a bit. Thanks
Edit: okay, maybe not 1/16", but at least 1/32".

Sounds like the barrel nut is loose. You may or may not have to pull the gastube to get it in spec.

Thanks for your replies. Based on my limited knowledge, that was the best I could hope for, and was kind of what I expected. I don't have time for it right now, maybe tomorrow before work. So I'm imagining that I remove the gas tube, using a little dinky punch (1/16"?), then tighten the nut using what tool? I will look at some of the tutorials before bed. Thanks

Well, that's Colt for ya'.

Quoted: Thanks for your replies. Based on my limited knowledge, that was the best I could hope for, and was kind of what I expected. I don't have time for it right now, maybe tomorrow before work. So I'm imagining that I remove the gas tube, using a little dinky punch (1/16"?), then tighten the nut using what tool? I will look at some of the tutorials before bed. Thanks

You will need a barrel wrench to tighten the barrel nut and a receiver block to keep it all in place.  Definately worth the money to get the right tools.

www.bushmaster.com/shopping/gunsmith/om-003.asp

www.dpmsinc.com/10Expand.asp?ProductCode=TL-MW

Quoted: Well, that's Colt for ya'.

"Quality makes it a Colt"

Well, the tools are on their way. I wondered why my AR was more accurate than my AK at 50yds, but at 100 the AK took over! I'm betting this'll fix it.

My JT worked loose at about 1000 rnds.  Rather than send it off, I just took the gas tube out with a homemade punch and a vice with rubber tubing around the tube, then tightened the nut with a pair of 36" inch pipe wrenches.  I used towels to protect the recievers.  The barrel nut got chewed up on the tips of some of the teeth, but not enough to hurt anything.  A spanner wrench would work if it ever had to be taken apart...which will never happen.

.....a pair of 36" pipe wrenches??????    I don't believe it!   Man, spend a few $ and get the correct tools to work on your rifle.  This thing isn't some rusty old pipe under your sink.

I had to do the same thing to my PWA with colt Sp1 upper!  Yes just punch out the roll pin in FSB and you may have a little resistance in pushing the gas tube out the back of the reciever!

I had to use vice grips(don't crush the gas tube)and a little tap with hammer on grips!

Then use the combination barrel wrench tool and a 1/2 inch breaker bar and crank it tighter(think around 40 to 80 pounds torque) but just enough for the gas tube to fit through the hole in the Delta ring and barrell nut holes!

Don't back off to make it fit(really just a good hand tap or knee pressure is all it takes) then put the gas tube back in stake the roll pin back!    And you should be good to go!!!

I know what I know from Tweak and this forum!!

Bob

Mine did the same thing , but before I tightened it I removed the brl nut to inspect it and found that they didn't put any moly grease on the threads. So I took care of that first before tightning it . Just my 2 sents. Might need to close up the notch a little while the brl is in to take out slop also.

I had the same thing happen to an upper I just bought (not a Colt) and you do need to tighten the barrel nut.  While I do not think you need to torque the barrel nut, I did in order to find out what was going on.
Tools needed: multi tool from DPMS $20.  DPMS upper block ($25).  Molly lube ($3).  Strap wrench (had, but IIRC about $10).
First, you will need to remove the gas tube.  I just removed the gas tube along with the front sight base/gas block as it all had to come off anyway.
What happened to me was when I tried to install a Phantom FS the barrel moved (about the 1/16th inch you saw), and the M4 feed ramps were out of allignment.
To break the barrel loose, it took 38 ft-lbs of torque.  Humm (they had lubed the barrel nut very well).
I tighted the nut back up, at 40 pounds the hole was alligned, but when I tried to install the Phantom again, again the barrel shifted.  OK, found the problem.
I tightened the barrel to 75 ft-lbs.  The next hole was ALMOST aligned.  I back it off and tightened again to 75, now it was closer, but not quite.  I did this 4 or 5 times and on the fifth try, at 75 pounds, the hole was aligned, but he feed ramp was off.  I took it loose again, put counter torque with a strap wrench on the barrel, tightened until the hole was aligned, screw the ft-lbs this time, and put the thing back together.  This time the M4 feed ramps were in alignement with the cuts in the upper and I put back on the Phantom FS without the barrel twisting.  
So, the company who made my upper did nothing wrong (which is why I will not tell anyone the name of the Company-they did offer to take it back and check it out but since I had all the tools I needed, crap, I could do that just as well as they could), they were within the torque specs, it was just not tight enough to keep the barrel from shifting while putting on the Phantom and crush washer.
I am in total agreement with HomoErectus about not needing to use a torque wrench for barrel installation, but in this case since it was a brand new upper, I wanted to see what the hell was going on and why my brand new barrel was shifting in the upper.

I've got mine disassembled now, and barrel removal required NO TOOLS!

Quoted: Mine did the same thing , but before I tightened it I removed the brl nut to inspect it and found that they didn't put any moly grease on the threads. So I took care of that first before tightning it . Just my 2 sents. Might need to close up the notch a little while the brl is in to take out slop also.

Ice Man, which notch is it you refer to? Where the index pin on the barrel fits? How would you close that up? Thanks

pair of 36" inch pipe wrenches

WoW!1

Yes, read this it was for front sight alignment but  you will get the idea!

[Quoted:]


--------------------------------------------------------------------------------




This is common. It's been covered in here before... but I cant find where I described the process..... You need to file open the right side of the upper receiver just a tad, where the barrel extension pin is located in the receiver slot. Then, using a center punch, stake the left side of the receiver slot, ever close to the edge, to "swell" the receiver in that location, just to the left of the barrel extension pin. This will *rotate* the barrel to the right, then torque the barrel back on. It takes a little playing, but using this method, you can get it centers perfectly. It really helps to use a laser boresighter in theis process. Unless your rear sight is all the way to one side, it probably is not worth it.... However, if you are comfortable with the process, you can get it smack dab centered, which is a great feeling!

Impossible, Colt is teh awesome!

Quoted: .....a pair of 36" pipe wrenches??????    I don't believe it!   Man, spend a few $ and get the correct tools to work on your rifle.  This thing isn't some rusty old pipe under your sink.

Well it was either my dad's aluminum pipewrenches or dont shoot in the DCM match the next day.  What would you do.  You sure cant get a spanner wrench by the next day when its already 8pm.

I didnt have any barrel spanner wrenches cause I bought my one any only upper already built so I didnt see the need for one.  How was I to know the barrel nut would work loose and I only discover it at the last minute.  

And while yes my rifles no pipe, its also not a safe queen.  I will never have a rifle i baby.  I will take care of them all, but I wont cry over scratches and dings.  Especially ones under the handguards.