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[ARCHIVED THREAD] - Barrel nut misalignment (Page 1 of 2)
Posted: 7/17/2014 7:24:30 PM EDT
Just got my upper back from Colt. I purchased a new 6920 back in March. I noticed the gas tube wasn't centered in between the teeth on the barrel nut which caused it to be uneven in the gas tube hole in the upper receiver, so it coudn't have room to float. I checked the fitment of the gas key/gas tube before shipping with the bolt removed and it was binding. I get it back and on the RO it says inspected and checked customer notes. The gas tube now seems to fit better onto the gas key but it still looks the same being off center. I guess they must have just bent it into alignment? I don't know. Just surprised they coudn't have just centered the gas tube into the upper receiver. Am I just being a picky complainer? 
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| No, you are not being picky or ignorant. You paid good money for it and it should be right. Some of us have complained about Colt's quality control in the past few months. Colts have always been good guns but I've seen what happens when companies let their QC slip. This is the reason I have a DPMS. I went to buy a Colt and when I saw the two my lgs had in stock, I changed my mind. Very happy I did. I realize I'll probably be accused of blasphemy, but they should take it back and make it right. |
| A little under 200 rounds through it, functions fine. I am just concerned with premature wear on the gas tube which from what I hear can lead to short stroking, the gas tube losing a good seal in the gas key because of one side of the mushroom flattening. BTW, it took over two months to get it back, seems like a fairly excessive period of time for an inspection. I know they are probably swamped, but still. |
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Can you move the gas tube left to right on the receiver end, or is it slaved one direction due to the barrel nut? If it moves freely left and right, it may just be tweaked. If you don't want to attempt tweaking (bending it) to get it aligned, or waiting 2 months to get your upper back, why not just buy a carbine length gas tube with roll pin from BCM for $13.00 and change it out?
Just a suggestion. Good luck and keep us posted! |
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Quick procedure overview if you decide to save time and do it yourself:
Gas Tube Inspection and Adjustment:  </a>" />
Gas Tube Removal:  </a>" />
Gas Tube Installation:  </a>" />
http://www.bravocompanyusa.com/AR15-carbine-gas-tube-p/gas%20tube%20-%20carbine.htm |
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Has some wiggle room to the left, none to the right. Ya, that make things a little more complicated, because if it won't move at all in one direction, then it is bound by the Barrel Nut, like you said. Any chance that you can post pictures with the hard guards off, so we can check it out? Thanks in advance, good luck and keep us posted. |
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If the gas tube in contacting the barrel nut, it WILL eventually fail. The barrel flexes slightly with every shot, it will get a hole worn in it. Have them fix it. Has anyone documented this actually happening or is this a hypothesis of yours? I have never seen or heard of a punctured gas tube due to physical wear from barrel nut interference. |
| I wouldn't take the chance of parting with my rifle for another two months. I'd fix it myself. They may have hit 80 Ft/Lbs of torque and can't go far enough to time it right, in which case it needs a shim. I've never used a shim for timing issues, so I can't speak to how they go on. |
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I wouldn't take the chance of parting with my rifle for another two months. I'd fix it myself. They may have hit 80 Ft/Lbs of torque and can't go far enough to time it right, in which case it needs a shim. I've never used a shim for timing issues, so I can't speak to how they go on. There are other ways of correcting that issue without using a shim. The receiver face can be lapped and trying another barrel nut usually helps. |
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Yep, and this is what happens when they start selling them for 800 bucks.
Having a misaligned gas-tube from the factory is crap. It takes a few seconds to fix for the assembler by just reassessing torque. But, it takes a little extra time on each gun to get it perfect. Cutting out this extra time to save money is my guess. |
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The tube should be centered between the teeth on the nut.
However if the gas tube is properly lined up to the gas key then good luck getting Colt to fix the nut alignment. You can fix it yourself, but you will be taking a chance on voiding the warrantee especially if you do something like lapping the upper. |
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I have shot an M4 with the flare on the receiver end of the gas tube completely gone. The end was actually tapered, and I NEVER had a cycling issue. I fee the whole "If the flare wears, it will leak gas and short stroke" thing is a bit exaggerated.
Ideally, there should be no contact or rubbing between the gas tube and the carrier key, but if there is, as long as the gas tube can move freely left and right (or at least in the direction that will align it with the key), then there should not be an issue. Obviously, it should not BIND or display excessive friction against the key. That said, like is stated above; Shoot it, and if stuff starts looking like it has unusual wear, replace the gas tube for $13.00 or send it back to Colt. |
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Has anyone documented this actually happening or is this a hypothesis of yours? I have never seen or heard of a punctured gas tube due to physical wear from barrel nut interference. Quoted:
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If the gas tube in contacting the barrel nut, it WILL eventually fail. The barrel flexes slightly with every shot, it will get a hole worn in it. Have them fix it. Has anyone documented this actually happening or is this a hypothesis of yours? I have never seen or heard of a punctured gas tube due to physical wear from barrel nut interference. Just common sense,......think about it |
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Just common sense,......think about it Quoted:
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If the gas tube in contacting the barrel nut, it WILL eventually fail. The barrel flexes slightly with every shot, it will get a hole worn in it. Have them fix it. Has anyone documented this actually happening or is this a hypothesis of yours? I have never seen or heard of a punctured gas tube due to physical wear from barrel nut interference. Just common sense,......think about it You can rationalize this comment as common sense, but that doesn't make it true or real. HAS IT EVER HAPPENED? If not it is just imagination and this is how internet half-truths and rumors get started. As an engineer I deal in facts and realities, not imagined issues. Show me the facts that back up your statement and then we can discuss it. Until then I think we can agree that your comment has no veracity. ETA: At this point we have 60+ years of experience with the AR type rifle design. If this were an issue it would it would be known by now. |
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You can rationalize this comment as common sense, but that doesn't make it true or real. HAS IT EVER HAPPENED? If not it is just imagination and this is how internet half-truths and rumors get started. As an engineer I deal in facts and realities, not imagined issues. Show me the facts that back up your statement and then we can discuss it. Until then I think we can agree that your comment has no veracity. ETA: At this point we have 60+ years of experience with the AR type rifle design. If this were an issue it would it would be known by now. Quoted:
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If the gas tube in contacting the barrel nut, it WILL eventually fail. The barrel flexes slightly with every shot, it will get a hole worn in it. Have them fix it. Has anyone documented this actually happening or is this a hypothesis of yours? I have never seen or heard of a punctured gas tube due to physical wear from barrel nut interference. Just common sense,......think about it You can rationalize this comment as common sense, but that doesn't make it true or real. HAS IT EVER HAPPENED? If not it is just imagination and this is how internet half-truths and rumors get started. As an engineer I deal in facts and realities, not imagined issues. Show me the facts that back up your statement and then we can discuss it. Until then I think we can agree that your comment has no veracity. ETA: At this point we have 60+ years of experience with the AR type rifle design. If this were an issue it would it would be known by now. Has it not ever happened? Thirty years as an aircraft technician, 15 years holding an FAA A&P license. Engineers have told me a lot of shit that could not happen......that did! Congrats on being an engineer,......but that does not mean squat! |
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Has it not ever happened? Thirty years as an aircraft technician, 15 years holding an FAA A&P license. Engineers have told me a lot of shit that could not happen......that did! Congrats on being an engineer,......but that does not mean squat! Quoted:
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If the gas tube in contacting the barrel nut, it WILL eventually fail. The barrel flexes slightly with every shot, it will get a hole worn in it. Have them fix it. Has anyone documented this actually happening or is this a hypothesis of yours? I have never seen or heard of a punctured gas tube due to physical wear from barrel nut interference. Just common sense,......think about it You can rationalize this comment as common sense, but that doesn't make it true or real. HAS IT EVER HAPPENED? If not it is just imagination and this is how internet half-truths and rumors get started. As an engineer I deal in facts and realities, not imagined issues. Show me the facts that back up your statement and then we can discuss it. Until then I think we can agree that your comment has no veracity. ETA: At this point we have 60+ years of experience with the AR type rifle design. If this were an issue it would it would be known by now. Has it not ever happened? Thirty years as an aircraft technician, 15 years holding an FAA A&P license. Engineers have told me a lot of shit that could not happen......that did! Congrats on being an engineer,......but that does not mean squat! gas tube is probably harder than the barrel nut |
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Has it not ever happened? Thirty years as an aircraft technician, 15 years holding an FAA A&P license. Engineers have told me a lot of shit that could not happen......that did! Congrats on being an engineer,......but that does not mean squat! Quoted:
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If the gas tube in contacting the barrel nut, it WILL eventually fail. The barrel flexes slightly with every shot, it will get a hole worn in it. Have them fix it. Has anyone documented this actually happening or is this a hypothesis of yours? I have never seen or heard of a punctured gas tube due to physical wear from barrel nut interference. Just common sense,......think about it You can rationalize this comment as common sense, but that doesn't make it true or real. HAS IT EVER HAPPENED? If not it is just imagination and this is how internet half-truths and rumors get started. As an engineer I deal in facts and realities, not imagined issues. Show me the facts that back up your statement and then we can discuss it. Until then I think we can agree that your comment has no veracity. ETA: At this point we have 60+ years of experience with the AR type rifle design. If this were an issue it would it would be known by now. Has it not ever happened? Thirty years as an aircraft technician, 15 years holding an FAA A&P license. Engineers have told me a lot of shit that could not happen......that did! Congrats on being an engineer,......but that does not mean squat! Stay on topic and quit with the personal attacks. You made a statement that this issue (Barrel Nut Misalignment) would cause the gas tube to be worn through at the contact point and I simply want you to show us when this has ever happened or been an issue. If not that it isn't an issue and is just BS. |
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That was my thought. It almost certainly is. Quoted:
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gas tube is probably harder than the barrel nut That was my thought. It almost certainly is. You can remove the almost from your comment. It is harder, and that's why I said what I did in the beginning. |
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You can remove the almost from your comment. It is harder, and that's why I said what I did in the beginning. Quoted:
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gas tube is probably harder than the barrel nut That was my thought. It almost certainly is. You can remove the almost from your comment. It is harder, and that's why I said what I did in the beginning. Calm down, I'm agreeing with you. No need to get all uppity. |
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Calm down, I'm agreeing with you. No need to get all uppity. Quoted:
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gas tube is probably harder than the barrel nut That was my thought. It almost certainly is. You can remove the almost from your comment. It is harder, and that's why I said what I did in the beginning. Calm down, I'm agreeing with you. No need to get all uppity. Not uppity at all. Sorry if it came across like that. |
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you guys do what you want to your guns, personally i align the gas tube through
the barrel nut correctly EVERY time. it should not be binding, it should go into the gas key without contacting one side or the other. I will break the threads a few times before a final torque, and use heat on the nut only if it helps to get it on easier/tighter to get the alignment right. for me there is no "good enough" its either correct or it isnt. |
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Stay on topic and quit with the personal attacks. You made a statement that this issue (Barrel Nut Misalignment) would cause the gas tube to be worn through at the contact point and I simply want you to show us when this has ever happened or been an issue. If not that it isn't an issue and is just BS. Barrel nut damaging the gas tube IS on subject! No personal attack there. Your being an engineer carries no weight. Common sense, parts rubbing on each other, one will fail. You can wear an anvil down with sand, a barrel nut could and will wear a gas tube. Stainless is a great deal softer than the nut. |
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If barrel nuts actually wore holes in gas tubes, it would be the topic of more threads than barrel nut grease, checking headspace, or lately, the Sig brace on AR pistols. So far as I can tell, it is not. Most smart builders adjust the barrel nut to the PROPER position, this not allowing the gas tube to contact the nut. There are not a great deal of reports of this because of proper assenpmbly. |
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you guys do what you want to your guns, personally i align the gas tube through the barrel nut correctly EVERY time. it should not be binding, it should go into the gas key without contacting one side or the other. I will break the threads a few times before a final torque, and use heat on the nut only if it helps to get it on easier/tighter to get the alignment right. for me there is no "good enough" its either correct or it isnt. Thank you! Someone sees the problem at hand and the correct fix! |
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Or it's a non-issue in the real world and you're just pushing an opinion with no factual basis. Quoted:
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........................There are not a great deal of reports of this because of proper assenpmbly. Or it's a non-issue in the real world and you're just pushing an opinion with no factual basis. Are any of your gas tubes in such a bind, and not free floating in the notch? I suspect (yes, opinion) that those of us that either inspect, or have assembled our rifles would not accept the tube being in a bind with the nut. For the casual shooter, it would probably never be an issue over the life off the rifle. I am just surprised that we would accept this as being normal, seeing as it is such a quick fix for the insurance that it may provide. |
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Are any of your gas tubes in such a bind, and not free floating in the notch? I suspect (yes, opinion) that those of us that either inspect, or have assembled our rifles would not accept the tube being in a bind with the nut. For the casual shooter, it would probably never be an issue over the life off the rifle. I am just surprised that we would accept this as being normal, seeing as it is such a quick fix for the insurance that it may provide. Quoted:
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........................There are not a great deal of reports of this because of proper assenpmbly. Or it's a non-issue in the real world and you're just pushing an opinion with no factual basis. Are any of your gas tubes in such a bind, and not free floating in the notch? I suspect (yes, opinion) that those of us that either inspect, or have assembled our rifles would not accept the tube being in a bind with the nut. For the casual shooter, it would probably never be an issue over the life off the rifle. I am just surprised that we would accept this as being normal, seeing as it is such a quick fix for the insurance that it may provide. Thanks for the question. I don't mean to imply that the misalignment is OK at all. You are right, it is easy enough to fix and should be done correctly. I just don't believe that the nut is going to wear a hole in the tube as described. |
| What caused the gas tube to be misaligned in the first place that caused the O.P had to send the rifle back the first time? Was a canted front sight? A bent gas tube? Upper out of spec? The "barrel nut bend fix" is a low-brow fix, fixing a defect with some modified hack assembly . |
| Am I missing the picture of how poor the alignment is? I've seen horrendous gas tube wear from them being out of alignment, but only a handful of times out of all the MIL and LE weapons I've shot and worked on as an armorer. In one case, the failure was immediate with the tube, in the second, the alignment was off by enough to cause severe wear on one side of the tube where it contacts the carrier key (massive round count on the weapon which also had peening on the locking lugs). I have never seen or heard of the gas tube failing or having wear as a result of contact with the gas tube and barrel nut. That doesn't mean it can't occur, but there is no doubt in my mind the wear would occur where the gas tube flare meets the carrier key WELL before there was anything at the point of contact with the barrel nut. |
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you guys do what you want to your guns, personally i align the gas tube through the barrel nut correctly EVERY time. it should not be binding, it should go into the gas key without contacting one side or the other. I will break the threads a few times before a final torque, and use heat on the nut only if it helps to get it on easier/tighter to get the alignment right. for me there is no "good enough" its either correct or it isnt. I love a well built stock factory rifle, Colt, Spikes, BCM, etc... But after building my last (3); I totally agree with you. I can take an infinite amount of time assembling a rifle to get everything as perfect as humanly possible. A factory rifle assembler has a quota to meet and orders to fill. He/she cannot possibly take as much time as I can. This is why I build my/friends rifles as oppose to buying complete rifles. I get exactly what I want with fantastic parts and the configuration I want, nothing that I don't. That said I would have no problem purchasing a KAC SR 15 for a good price... |
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First off, quoting one's credentials here doesn't carry much weight. Engineer, scientist, metallurgist, whatever...there's enough history of someone from any profession being wrong enough that saying "I'm an X" really doesn't sway folks here. Sad but true, and I think part of it is influenced by the fact that on the Internet, you can say you're anything. By which I mean ABSOLUTELY NO offense to anyone, but when someone says "I'm a brain surgeon and..." it really comes across as kind of fake. I am a retired Airman, a computer scientist, an Occupational Therapist, and an avid AR15 enthusiast, but those creds aren't going to convince anyone of anything, nor is my pointing out that I am a certified AR armorer.
On the other hand, pointing out HOW something might work or fail is often better than anything else. Stickman notes gas tube wear from the gas key due to misalignment, and that makes sense. On the other hand, how is a misaligned gas tube going to rub on the barrel nut? I can't see that happening. All I can see is the tube being deflected side-to-side by the gas key and maybe bouncing against the nut. There are two ways to ensure good gas tube alignment. The optimal way is to make the barrel nut PERFECTLY centered on the bore/upper's gas tube hole/gas key. That's best because it gives the tube the most room for vibration and avoids any angular movement that could wear or bend anything. But sometimes it's just too darn hard to get that last little bit of torque on the nut, and you're off by just a bit, so you either back off and try again, (or start over, maybe lapping the front of the upper if needed), or you leave it and try method two: bend the gas tube. The aim here is to bend the tube just enough to have it go straight through the upper so that the gas key goes over it as perfectly straight as possible. |
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You can remove the almost from your comment. It is harder, and that's why I said what I did in the beginning. Quoted:
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gas tube is probably harder than the barrel nut That was my thought. It almost certainly is. You can remove the almost from your comment. It is harder, and that's why I said what I did in the beginning. AFAIK, gas tubes are relatively soft stainless, while barrel nuts are relatively hard CM. Gas tubes are not supposed to be particularly hard, so that at the time of high pressure gas flow that the end of the tube expands a bit and creates a better seal against the key. |
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AFAIK, gas tubes are relatively soft stainless, while barrel nuts are relatively hard CM. Gas tubes are not supposed to be particularly hard, so that at the time of high pressure gas flow that the end of the tube expands a bit and creates a better seal against the key. Quoted:
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gas tube is probably harder than the barrel nut That was my thought. It almost certainly is. You can remove the almost from your comment. It is harder, and that's why I said what I did in the beginning. AFAIK, gas tubes are relatively soft stainless, while barrel nuts are relatively hard CM. Gas tubes are not supposed to be particularly hard, so that at the time of high pressure gas flow that the end of the tube expands a bit and creates a better seal against the key. i would be VERY surprised if the gas tube is expanding at that end |
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Quoted: AFAIK, gas tubes are relatively soft stainless, while barrel nuts are relatively hard CM. Gas tubes are not supposed to be particularly hard, so that at the time of high pressure gas flow that the end of the tube expands a bit and creates a better seal against the key. Quoted: Quoted: Quoted: Quoted: gas tube is probably harder than the barrel nut That was my thought. It almost certainly is. You can remove the almost from your comment. It is harder, and that's why I said what I did in the beginning. AFAIK, gas tubes are relatively soft stainless, while barrel nuts are relatively hard CM. Gas tubes are not supposed to be particularly hard, so that at the time of high pressure gas flow that the end of the tube expands a bit and creates a better seal against the key. |
[ARCHIVED THREAD] - Barrel nut misalignment (Page 1 of 2)
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