Gas tube longevity in original M16 compared to KAC/BRT

[JediGuy]

How often are gas tubes replaced on original 20” rifle length M16/AR15’s?

What about KAC with their extended system?

How does (or would one project) longevity on a BRT with the Optimum 16”? For that matter, would their 12.5” EXtended Carbine gas be expected to last longer than a 12.5” carbine system?

My question primarily is whether a longer gas system needs to have the gas tube replaced as often as carbine (or possibly midlength on 16”) systems. It seems that the gas tube is technically a wear part, but I thought I read that it really “wasn’t” on the original rifle. Is this an unfortunate feature resulting from Colt’s carbine system?

[markm]

Gas tubes almost NEVER need replacement unless it's a REALLY high volume fired gun. The ONLY time I've had gas tube issues is on the middy tubes. They seemed to have the bulb on the carrier end of the tube which would wear down fast and leak gobs of gas and carbon.

If your key alignment is good with the tube, the tube shouldn't be wearing out. Changing it after 20k rounds might be a preventative maintenance type of thing.

[Ned Christiansen]

In classes we find a lot of gas tubes that need replacing and no one knew until we looked for it. The big issue, really the only issue I that I have seen, is that the bulb-- I call it the knob but bulb is good too-- is worn. Why is it worn? Because the gas tube is misaligned and every time the carrier key telescopes over it, it's having to bend the gas tube into alignment..... a little, or a lot. "A little" means it wears out somewhat prematurely, probably. "A lot" means it wears out rather quickly.

Now, from the "little things mean a lot" department, a major contributing factor is a carrier key where manufacturer cut corners and it's rough inside where it 'scopes over the GT. Then it was chromed or nitrided. That creates the perfect tool for wearing out gas tubes. Add a gas bloc that's been installed a little off kilter, and this puts the GT off center in the upper receiver. Next time you have a gas block loose with the GT still installed, just put the gas block in place but then turn it side to side just a tad. You will see an out of proportion movement on the back end of the GT inside the upper.

Or it might just be a GT that is a little bent or a few other subtle things that make its alignment bad. I mean in the best of conditions, there will be some wear there because the GT is meant to float a little and of course the carrier is not a no-slop fit in the upper. They have to find each other every cycle, hence the chamfers on the end of the GT and the mouth of the carrier key spigot. But an no-bind, "no hitting" fit is optimal.

I've never seen a GT that had to be replaced due to something like blockage or erosion. I mean if there's one part of the gun that is truly self-cleaning, it seems to be the GT and the carrier key anywhere the abrasive-blast stream of gas has a clear path with no corners for stuff to build up.

I did run into a gun years ago that cycled very weakly. After looking for everything it could be, I had to look for things it could not possibly be.

Someone had Dremeled the bulb completely off, shortening the GT by 1/4"...... "Well there's yer dang problum, yer dang gas tube has a big ol' thing on the end of it-- it's too dang tight in that little hole!"

[robbins290]

Never had to replace one, but I always do a tube and BCG when i replace a barrel. I also never clean them or do any maintenance to them.

[MistWolf]

In classes we find a lot of gas tubes that need replacing and no one knew until we looked for it. The big issue, really the only issue I that I have seen, is that the bulb-- I call it the knob but bulb is good too-- is worn. Why is it worn? Because the gas tube is misaligned and every time the carrier key telescopes over it, it's having to bend the gas tube into alignment..... a little, or a lot. "A little" means it wears out somewhat prematurely, probably. "A lot" means it wears out rather quickly.

I've had to replace a couple three gas tubes because the knob was worn. Every time, the gas tube was of "Unknown Origin". Maybe they were softer than normal. They were carbine length gas tubes.

[lysander]

I've had to replace a couple three gas tubes because the knob was worn. Every time, the gas tube was of "Unknown Origin". Maybe they were softer than normal. They were carbine length gas tubes.

The tube is half-hard 304 stainless steel tubing.

That's not the most wear resistant stuff out there.

And' I wouldn't replace it with anything tougher, as a gas tube is cheaper and easier to replace than a carrier key (if it rubs, something has the wear).

[okie]

Never heard of a gas tube needing to be replaced. Pretty sure they always outlast the barrel, which they get replaced with.

[ST911]

A decent gas tube properly installed should last the barrel. Nubs may wear eventually. Replace with the barrel.

Gas tubes are more likely to need replacement because of people messing with them or improper installation.