View Full Version : Colt Carbine Barrel Movement
I have a very early post-ban Colt Government Carbine.
There is a slight, very slight, movement when the FS is twisted back and forth. Just enough for me to notice it. None of my other rifles have any movement. The FSB is tightly attached and the Delta ring has good tension.
I have not yet fired the rifle. Is this movement something I should be concerned about?
Thanks.
I have a very early post-ban Colt Government Carbine.
There is a slight, very slight, movement when the FS is twisted back and forth. Just enough for me to notice it. None of my other rifles have any movement. The FSB is tightly attached and the Delta ring has good tension.
I have not yet fired the rifle. Is this movement something I should be concerned about?
Thanks.
Yes. Sounds like the barrel nut is all but come off, but I wouldn't know how this is possible with the gas tube in the way. Weird.
Have you fired it before? My guess is that it was not torqued properly (assuming no one else has played around with it) and since the tube doesn't sit right on the nut this would allow for some play over time.
Have you fired it before? My guess is that it was not torqued properly (assuming no one else has played around with it) and since the tube doesn't sit right on the nut this would allow for some play over time.
No, I have fired it yet. The gas tube is well situated in place. The closest way I can describe the situation is like a 1911 slide that has just a little bit of play in it. For a 1911, this adds to its reliabilty, with an AR, I'm not so confident.
No, I have fired it yet. The gas tube is well situated in place. The closest way I can describe the situation is like a 1911 slide that has just a little bit of play in it. For a 1911, this adds to its reliabilty, with an AR, I'm not so confident.
You do mean the barrel itself is wiggling in the upper? No, this is not about "reliability" this is about something not being right at all.
This is the type of movement I am experiencing. I may have even exagerated the amount of movement, but it gives you the concept.
http://i70.photobucket.com/albums/i90/TedG954/Presentation1.jpg
I think you're feeling upper/lower play which is completely normal.
Ok, real simple. Remove the handguards and separate the upper and lower. Grasp the FSB and the forward part of the carry handle or receiver. Twist the upper and FSB in opposite directions. if there is movement then something is wrong.
I would also grab the barrel nut and see if it moves at all. It shouldn't.
No, I have fired it yet. The gas tube is well situated in place. The closest way I can describe the situation is like a 1911 slide that has just a little bit of play in it. For a 1911, this adds to its reliabilty, with an AR, I'm not so confident.
Is it a Colt marked barrel?
In an armory of less than 200 rifles, I've run into at least 3 Colt M4s that have worked their barrel nuts loose over the years (they were probably improperly torqued from the factory). These were all high round count rifles, but it definitely happens.
Do what 'gunz says.
If the bbl nut is tight, the other possibility is that the barrel extension is loose.
TX Rancher
10-20-11, 07:34
I have a Knight that did the same thing. In my case the barrel nut was loose. All I did was re-torque it and it's fine now.
By the way, it was the original barrel that came with the rifle. I suspect it wasn't torqued right at the factory. Not a slam at Knight, every manufacturer has something escape their factory every now and then.
In an armory of less than 200 rifles, I've run into at least 3 Colt M4s that have worked their barrel nuts loose over the years (they were probably improperly torqued from the factory). These were all high round count rifles, but it definitely happens.
I can't see how a barrel nut can work loose with the gas tube preventing it from moving. :confused:
Sometimes threads will bind up and give a torque indication without seating correctly. After awhile, the threads let go and they'll be loose. That's why the manual tells you to torque the barrel nut three times and why it's important to use anti-seize
If you look at your tube on some it "hovers" just over the nut and doesn't exactly touch it. If it wasn't torqued correctly then I can see how it would loosen with vibration from shooting.
Picture it vibrating back and forth.
I can't see how a barrel nut can work loose with the gas tube preventing it from moving. :confused:
If you look at your tube on some it "hovers" just over the nut and doesn't exactly touch it. If it wasn't torqued correctly then I can see how it would loosen with vibration from shooting.
Wow. I've never seen one like that.
They aren't all like that, but some. I remember in A'stan we had a muj who couldn't qualify with is M4. When I checked it sure enough the barrel was loose. I tightened it up and we sent him back out and he was able to shoot better (still failed to qual though).
Wow. I've never seen one like that.
You can lead a muj to m4, but you can't make him qual!;)
The barrel nut was loose. I tightened it one by one notch and the movement stopped.
Thanks to all who offered advice!
In an armory of less than 200 rifles, I've run into at least 3 Colt M4s that have worked their barrel nuts loose over the years (they were probably improperly torqued from the factory). These were all high round count rifles, but it definitely happens.
We have had 25 patrol guns for the last 10 years and 2 guns have had the barrel losen up. (I don't include the SWAT guns since those were most definately altered from factory specs.) All of them are Colt 6920s. I think both were from our first batch of 15 or so bought in 2000. It could have been the same gun twice. The second time we bought a torque wrench specifically to tighten it. My advice was to send it to Colt since we did very little to the guns to put them into service, nothing that would have cause losening the barrel from the upper. Make them fix their foul up.
Thanks CACOP. This Colt was originally a patrol rifle and it is well over 20 years old. I think I have tightened the barrel.
May I ask how you tightened it and what was the torque set at?
The barrel nut was loose. I tightened it one by one notch and the movement stopped.
Thanks to all who offered advice!
May I ask how you tightened it and what was the torque set at?
I bought an armorer's tool (barrel wrench). I don't have a torque wrench, so I had to guess at the 30 lbs.
Ted,
30 lbs. is the minimum with 80lbs. being the max limit. I encourage you to do it correctly or you will have the same problem.
It needs to be secured properly and tightened.
I bought an armorer's tool (barrel wrench). I don't have a torque wrench, so I had to guess at the 30 lbs.
Ted,
30 lbs. is the minimum with 80lbs. being the max limit. I encourage you to do it correctly or you will have the same problem.
It needs to be secured properly and tightened.
I'll try to find a torque wrench. Thanks again.
For the record, I don't use one. But, I have done enough of them that it's not necessary.
I believe that many auto places like AutoZone, Schucks, O'Reilly, etc... have torque wrenches available.
I'll try to find a torque wrench. Thanks again.
I think I have tightened the barrel.
That's what the last installer said. :sarcastic: Keep an eye on it.
I have seen this enough times on factory rifles including Colt. 2 of our 65 Colt M4A1's had this happen over time. Somewhere in the 15-20K round count range. It is definitely a factory issue as the gas tubes and barrel nuts were never altered. Basically over time the barrel nut loosens causing that exact very minor movement of the barrel that was mentioned by the OP. This results in impacts all over the target. Some mistake this as chamber or throat erosion but it can be a loose barrel nut.
The reasons that I feel that this happens is two fold. First where the alignment of the notches start on the stock USGI type barrel nuts in relation to the gas tube. Generally you set the torque to the low end of the spectrum and then torque to the next notch on the barrel nut for alignment. The problem here is that sometimes the torque is too far towards the low end on the initial tightening of the nut and going to the next notch is waay to far or too much torque, so the person assembling the rifle errs on to low of the torque spectrum. Of course we can solve this by working the threads or trying other barrel nuts.
This leads us to the second issue which I personally feel is good practice when doing the barrel nut and that is "working the threads". I feel, that working the threads, especially on dissimilar materials is important for final torque. Tighten to 35ftlbs loosen, tighten, loosen, tighten loosen then give it the final torque. You will see that the threads will "stretch" and that the alignment of the nut will shift during this process before setting final torque. This will invariably lead to a better final torque. If you don't pre-stretch the threads they can loosen. Kinda like re-torquing lug nuts on a vehicle. Time, movement, heat can cause issues. Far far less chance if you pre work the threads. As mentioned, someone who does a lot of mechanical type work has a good grasp of torque values without using a torque wrench. I will admit that this is not a common issue, but it happens often enough even from Colt, so working the threads is good insurance and isn't hard to do.
Check out one of my video's of the installation of the DD Omega X. Notice when I am working the barrel nut, where it ends up after working the threads. It sits "hand tight" with a good bit of further rotation after working the threads. At about 1:50 I start discussing the barrel nut alignment thing and working threads.
http://www.youtube.com/watch?v=Or7qwDAlMSQ&feature=related
My unit had a rash of these with A2s. First indicator was rilfes failing to group during zero. Checked barrel tightness and it felt like just a slight "click" when twisted. After that we made it part of operator inspection whenever cleaning and wound up re-tightening about 20 rifles.
Tighten to 35ftlbs loosen, tighten, loosen, tighten loosen then give it the final torque
Also per the 23&P p. 015-15 (http://www.coschooloffirearms.com/23plevelm16m4.pdf)
Agree with the others. Remove and reinstall the barrel per the manual, rather than simply tightening it down. It's not an accessory screw, and needs to be done properly.
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