View Full Version : Is a gas tube just a gas tube?
I have learned much from reading about the various types of parts and the importance of their quality on the forms. For all of you contributors, please accept my thanks.
However, I've now progressed to the point where I need to procure a gas tube (mid length) to go on my centurion arms barrel. So... is there really any difference in these things, or are they all made by just a few firms? I can't really see how they would be all that different. Ok, I can _see_ how they would be different, but are they, as a practical concern?
Anyway, I need one, and would to prefer to buy only one... :-)
Your thoughts?
Just buy from a reputable dealer like G and R or Bravo.
I don’t know if there is a difference or not but like other AR parts there probably is.
I don't know about gas tubes...I've just assumed they were all pretty much the same, but I always buy mine from BCM.
I do know that getting an actual gas tube roll pin punch was kind of a revelation for me. That was $5 well spent....
There are differences. Over the years I've seen tubes missing the key flange, different lengths of tubes, some twisted or contorted, and some fail at low temps and intervals. All were from the usual suspects.
I'm not an expert on gas tubes, and don't really feel like pouring a great deal of time and research into them.
For that reason, I've bought all of mine from Bravo Company.
That is a excellent question & I always assumed they were all the same.
We all know what happens when we assume!
Awaiting input from some of our industry professionals & those who wrench on them daily.
The temp would ruin a heat treat.
Edited because I got my gauges mixed up. Should be .06 wall thickness.
There are differences. Over the years I've seen tubes missing the key flange, different lengths of tubes, some twisted or contorted, and some fail at low temps and intervals. All were from the usual suspects.
This. I can tell the good ones by feel, but not much else. I am sure there is a TDP spec on them and will see if I can look it up.
C4
That is a excellent question & I always assumed they were all the same.
We all know what happens when we assume!
Awaiting input from some of our industry professionals & those who wrench on them daily.
Nothing is ever "all the same" when dealing with AR parts. :D
C4
Nothing is ever "all the same" when dealing with AR parts. :D
C4
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FWIW, expounding on what Grant said...
In my Plant, we use standard size SS tubings: 1/8", 1/4", 3/8",... We also have to specify the material, wall thickness, welded or seamless, etc. So, I spent a little time investigating an AR Gas Tube by its dimensions.
I mic'd my two AR's Gas Tubes at .1785" to .179".
I found a .180" SS Tubing to be listed in several places, so for simplicity, I am going to assume that this .180" tubing is a "nominal” size and is used for Gas Tubes. (Which is probably correct since the TOL listed in the Table bring it almost up to the exact size.)
In the Table below, tt looks like the .180” OD tubing is called a “7 gauge” and there are 5 different wall thicknesses listed.
http://i54.tinypic.com/24l6how.jpg
In the Table there are 5 different ID’s for the same .180" OD tubing. Then, add in 8 different stainless steels available and then, you can get the tubing either welded-seam or seamless. A better grade of SS will cost more, as does thicker walls, as does a seamless tube.
So, with as much unscrupulous dealing we have seen in the “AR” industry the past few years, it would not surprise me in the least, if someone is out there selling a low-grade of SS welded-seam thin-wall .180" OD tubing as "mil-spec" Gas Tube.
So, after saying all of that...I would say that there could definitely be a huge difference in Gas Tubes.
But maybe it’s just me…
.
So....there's a (potential) variability in gas tube quality. I don't know the answer...is gas tube failure a pretty common thing?
So....there's a (potential) variability in gas tube quality. I don't know the answer...is gas tube failure a pretty common thing?
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I remember seeing a video clip of a test where something like 30+ 30-round mags were fed one after the other into an AR on full auto.
IIRC, the Gas Tube is what failed. Caught the handguards on fire but the gun still fired a few more hundred rounds.
But that was a pretty extreme example.
.
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I remember seeing a video clip of a test where something like 30+ 30-round mags were fed one after the other into an AR on full auto.
IIRC, the Gas Tube is what failed. Caught the handguards on fire but the gun still fired a few more hundred rounds.
But that was a pretty extreme example.
.
Yeh, I've seen a couple of those. On one the handguard was actually on fire but still going full auto til the gas tube went TU and they went to single shot. On the other, the gas tube was fine but the barrel melted then blew up. IIRC, they were both done in the Colt factory.
Yeh, I've seen a couple of those. On one the handguard was actually on fire but still going full auto til the gas tube went TU and they went to single shot. On the other, the gas tube was fine but the barrel melted then blew up. IIRC, they were both done in the Colt factory.
Probably also had rounds cooking off o.O I wonder what the spec for the LSW is.
So....there's a (potential) variability in gas tube quality. I don't know the answer...is gas tube failure a pretty common thing?
Complete/catastrophic failure isn't as common as the lesser observations listed. They're most easily induced in burst or auto guns, or semis running hard.
Failure of the tube results in the gun stopping. Hot gas may burn the shooters hands, face, or eyes, depending on the particulars. Sometimes they will simply heat up, distort or have a small leak, then stop the gun.
Complete/catastrophic failure isn't as common as the lesser observations listed. They're most easily induced in burst or auto guns, or semis running hard.
Failure of the tube results in the gun stopping. Hot gas may burn the shooters hands, face, or eyes, depending on the particulars. Sometimes they will simply heat up, distort or have a small leak, then stop the gun.
Yes, I realize all this. But what we're talking about here is variations in gas tube quality and what I'm curious about how often they fail in normal use, let's say TAC Team use. Not leaks at the gas block, nor damage from misalignment with the gas key, but a ruptured tube because the wall thickness is too thin or the seam weld is crappy.
Is that a pretty common thing? Have you seen that happen?
It has to have a specific ID, .120~, that is why they wont drill your gas port any larger than that. It has a specific OD because the gas key has to fit over it. OD-ID = thickness. Seamless tubing is cheaper than welded usually.
If you took all the gas tubes ever in existence, and made a chart of their lifespans. It would look like a U. Failure rate "in normal use" (the random rate) is always lower than it is on first use or at the end of it's lifespan. (This concept is practically universal btw) :p
good job, guys... now PWS is gonna come out with an "improved" gas tube. it'll be ribbed, chrome-lined, have a Picatinny rail section, and telescoping, for use with "mission adaptable" adjustable gas lengths (forthcoming).
Titanium would be better.
I notice that there isn't an entry for an ID of .120 in the chart posted by UCRT. Significant? I'm not knowledgeable enough to say.
Those are hypodermic tubing gauges. http://www.connhypo.com/pages/sub05_toc01.html
My searching has yielded nothing but questions. I saw someone post that his search fu was not working. I think my fu may have been foo'd by his...
Regardless, the only thing I found was that the TDP is "not available on the internet.". Is there a way I can find this data?
And FYI, I'm now on an info quest, this is not about "where to buy" a gas tube:-)
Thanks all, for the good discussion.
justin_247
03-19-11, 18:37
good job, guys... now PWS is gonna come out with an "improved" gas tube. it'll be ribbed, chrome-lined, have a Picatinny rail section, and telescoping, for use with "mission adaptable" adjustable gas lengths (forthcoming).
HA HA HA! Hate to say it, but...
Spike's beat them to it this time. They have a melonite treated gas tube that they use on their 5.45 mm upper receivers.
It's a pretty good idea for corrosive ammo, actually.
Those are hypodermic tubing gauges. http://www.connhypo.com/pages/sub05_toc01.html
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I think it is quite possible that some type of hypodermic tubing might be what an AR uses...but that is just speculation.
Generally, a designer will try to use what is already available unless there is some unique set of circumstances that requires a special design, which raises the price. For a Gas Tube to sell for $10, it can't be too exotic.
I’ve seen this commonality of parts on 20k+ hp motors; axial, recip, & centrifugal compressors; gas turbines; steam turbines; etc. I’d reckon there isn’t a “special” diameter for AR’s, just a spec for a certain temperature and pressure but again…speculation.
FWIW
Here's a LINK to McMaster-Carr’s (http://www.mcmaster.com/#catalog/117/129/=bi8il2) catalog page about hypodermic tubing.
But maybe it's just me...
.
Cesiumsponge
03-19-11, 22:20
Titanium would be better.
Titanium doesn't always make everything better by default. Seems the gas tube is very low on Murphy's list, hence the difficulty in finding a reoccurring method of failure where the gas tube was the primary cause. It's probably why manufacturers have left it alone.
Robb Jensen
03-19-11, 22:28
I use BCM or Colt so I don't have to do research on who's gas tube is GTG.
edit @ucrt
was thinking more like http://plymouth.na4.acrobat.com/stainlessspecs/
Since AR was an aircraft company and the wall sizes are closer.
Titanium doesn't always make everything better by default. Seems the gas tube is very low on Murphy's list, hence the difficulty in finding a reoccurring method of failure where the gas tube was the primary cause. It's probably why manufacturers have left it alone.
It was sarcastic :p Mostly. It also has better heat tolerance. If I was trying to think of a fast way to make AR more reliable in full auto I would say open bolt.
HA HA HA! Hate to say it, but...
Spike's beat them to it this time. They have a melonite treated gas tube that they use on their 5.45 mm upper receivers.
It's a pretty good idea for corrosive ammo, actually.
I have got to see this. Could you post the link since i can not find it on their websit.
I have got to see this. Could you post the link since i can not find it on their websit.
I've only seen it complete with the 5.45 upper...the entire thing is treated with Melonite...AIM sells them...
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