How long should a gas tube last? What are some signs that this may need to be replaced. Also… would it be possible to remove a gas tube on a 14.5 without removing flash hider?
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As far as a Gas Tube lasting…Worst case …
… a Gas Tube will last about 900 rounds (30 FA mag dumps in <5-mins)
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But that is worst case. Besides that…they seem to have a very long life - ??
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geez, what is that, one of those crappy colts? I can’t believe those handguards suck that much…
I don’t think there is an established life of a gas tube under regular conditions. Yes, you can remove a gas tube by simply punching the roll pin out, grasping the tube and pushing it slightly rearward and then pulling forward. However, depending on various factors you may need to use some vise grips to remove the tube.
I had one that was so caked into place I had to cut the tube and yank it out.
Signs of a gas system problem (bolt rings, carrier key or gas tube) being worn would be short stroking and sluggish operation.
Gas tube should outlast the barrel under reasonable firing rates.
There was one imbecile on another forum who regularly melted gas tubes on his drop in autoseared ARs. But other than that kind of retardation, normal use won’t wear it out.
mark m has it right under normal semi auto use they will last the life of the gun.
The only real wear item on them is the ‘mushroom’ at the end. If the tube is mis-aligned, it will wear at an accelerated rate and could cause loss of pressure.
That’s a good point. I have some that are pretty smoothed out and still work… but a borderline cycling gun might be bothered by it.
Question for the experts here. I will soon be in the process of installing a DD RIS II FSP rail on my BCM carbine and since it requires complete disassembly of the upper I am curious if I can reuse the gas tube assuming it is not damaged by removal, or should I cough up the $13 and buy a new one? I don’t see why I couldn’t use the old one but I want a second opinion and this seems like the perfect thread to ask so I don’t have to start a separate thread.
You can. I replaced mine when I rebuilt the upper for the simple fact that I was starting with a fresh barrel and rail. I checked my headspace and reused the old bolt simply because I want to see how may rounds I can go before it should fail.
I would recommend removing it and soaking it in some Mpro-7 or something to break up and loosen any carbon inside.
Thanks for the info IG. I won’t be using a new barrel or bolt, I am simply taking apart the OEM BCM components and putting them back together. The only thing changing is the handguard (replacing KAC RAS with DD) and the barrel nut but otherwise it should be good-to-go with the old gas tube. I already have to buy a couple tools to do this so that’s 13 bucks saved by not having to buy a gas tube. Thanks again.
Gotcha. I was just stating why I did it. In your case if you know that there haven’t been a shit ton of rounds through it then by all means r-use. If you are taking it apart anyways- unless you are in a hurry it can’t hurt to soak it overnight in something.
I don’t know what the true life span of a carbine gas tube is, but I replaced mine a couple of months ago, (after just over 10,000 rounds and 3 barrels), and it was burned through opposite the gas vent hole. The hole was only about .0015 in dia., and kind of oblong.
Gun still worked fine, though. I guess I should have gotten after it sooner, because it was just about welded into the gas block from all the carbon build up. The gas block didn’t seem damaged, so I re-used it. So I would say something less than 10,000 rounds is the correct answer. I do keep a log book on this rifle, so the round count is accurate, if anyone cares.
I’m bumping this ancient thread because I just lived this exact scenario.
My BCM 14.5 Middy wasn’t locking back on mild .223 ammo… and kind of chunking along sluggishly.
I got to looking at the gas tube and it had NO step up/mushroom on the end of it… and the carbon fouling was running 3 inches forward of the gas key on the outside of the tube.
The spec on a new gas tube is 0.180". I measured a used rifle tube on my bench, and it was about 0.175". The tube in my middy was 0.170" with spots that were even lower.
I replaced the tube and the gun came back to life. I can’t tell if the tube has always been out of spec or if the gas key wore it out. The gun only had about 1500-1600 rounds through it.
On the subject of gas tubes, Ive always wondered what an “enhanced gas tube” is. How is it different, are they worth putting on a SHTF rifle? Also, what about the melonite coated ones? Better, worse, no diff? I THINK I remember in the video of the 900 rounds
being fired at once, somewhere in the description it said the rifle had an enhanced gas tube, I dont know if it was needed to fire that many rounds or not.
Mark,
One thing I do on a build it try and tweak the gas tube as much as possible to not resist the carrier moving forward.
I do this with the upper upside-down as the magazine cartridge column forces the Bolt Carrier against the inside top of the reciever (wear patterns will confirm this).
I want a lubed BC only to close at the lowest possible incline with the least felt transition over the tube as possible.
I tweak under the handguards and the end if necessary.
The carbine length tubes are most critical as they are the shortest (ignoring pistol as I have no desire to fool with those abominations).
The longer the tube, the better it flexes and ‘guides’ into the key with lesser resistance. The shorter the gas tube,the straighter the shot you need to try and achieve. Shorter tubes have a greater diameter vs. length and are stiffer in comparison.
Feel the tube lightly with the tip of a finger as it slides into the mouth of the key. You can feel the direction of the deflection if you are careful. also watch the tube right where it comes out of the reciever.
Also Mark, was the wear pattern asymeterical, I.E. greater on one side than the other?
The gas tube never appeared to have any binding before. And the weird thing is that there doesn’t appear to be any uneven wear. Either the key chewed up the whole gas tube evenly, or it never had the step up that seals in the key.
I’ll be watching the new key closely to see if there’s any strange wear.
I am the gas tube masta, probably the imbecile as well but no drop-ins.
I have learned that all gas tubes are not equal. I used to just order them from vendors and some had varying failures, now I just call up friends who are mfgers to get them. But even me, on a normal weapon that isn’t ported to all hell, you should be fine with a real tube.
I think it is the nickel content for the high thermal limits, and you can’t go on round count because the temperature reached depends on the time as well and the small mag change time changes this drastically and some change mags faster than others, Some stainless will yield at lower temps.
You should never have a real problem, I got a good one to last for about 20k of exhausting work, about 20-1k days spread over a year or so. It started short stroking, and it blew a hole in the gas tube right as it came out of the front sight base. I never could get the chunk out and it wasn’t worth it at that point. It made me realize that if you don’t change them one day you are going to be fighting that thing and it sucks.
Step up porting on a shorty barrel and you can really fail tubes much faster.
Inconel is the only enhanced tube you should ever consider as an option, inconel is a very high nickel material, it is a bitch to machine.
-I’ve seen some coated, not sure what that would do
-Fat boys are great if you know what you’re getting into, it is like adding a huge buffer, or having a gas leak somewhere. Definitely takes away power
-Pig Tails kind of like Fat boys but less robbing
Look at the original LMG from Colt.
they had a raised port exit from the sight base and ran a straight tube, it was .25" stainless that was turned down to the .188 on the ends.
That shape on the end is very important, it helps with a good fit and no bind.
I was thinking about that when I was searching the old threads on gas tubes. Guys were talking about the Spikes coated tube and how they didn’t want a shiney tube. :rolleyes:
Shoot! If my tube weren’t shiney, I’d never have noticed where all the excess gas leakage was coming from.