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…
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.
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.
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.
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.
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.
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)
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).
