does anyone here truly cleans AR-15 gas tube

Squirt of brake parts cleaner, muzzle down. Clean bore with Hoppe's or CLP.

Never had an issue, even when swapping a .22lr conversion kit in and out.

I have a 5.45x39 AR upper and shoot pretty much only cheap corrosive surplus ammo through it, I do flush the gas tube with hot soapy water, never needed anything more.

My nephew was in Army Special Forces for 10 years and an operator for 9 more years starting in the 1990's and spent a lot of time in both Iraq and Afghanistan and his favorite slogan is "If you don't clean your weapon the problem is self-correcting." Make of it what you will. If you don't have people shooting at you it probably doesn't really matter except for internet warriors.

Never.


Leave it alone.

Steel Horse Rider said:

"/QUOTE]"If you don't clean your weapon the problem is self-correcting./QUOTE]

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Meaning: Your weapon can/will malfunction and the enemy shoots you.

Like has been said, don't worry about cleaning the gas tube!

I seriously doubt any civilian will ever be firing tons of blanks or any other situation that can cause the gas tube to need cleaned.


I really enjoy this site for the civility among everyone. I know that asking about cleaning a gas tube is like asking what kind of oil to use in you vehicle. It can/does start arguments. This exact subject starts all kinds of trouble on other sites

The newest last on my long list list of things to do is cleaning the gas tubes on my AR's

I blow them out with very high pressure and hot gasses.

Nope

If, for some odd reason, you feel compelled to clean a gas tube, brake cleaner and swab bore. Even after shooting up the leftover blanks from FTX's, the gas tubes didn't need it. The barrel on mine did, after being heated red hot!, so I replaced the gas tube at the same time, but it was still working before I replaced it.

Pledge and a feather duster

Nope, never felt the need to.

I feel so alone in this thread. I ran a pipe cleaner through after about a year of shooting and I wish I took a picture of the junk it picked up.

Can't say it restricted anything cause the gun was operating normally, but it sure made me feel good when I was done. Maybe I will give it two years from now on. Then again, maybe not.

No real reason to clean a gas tube considering the 5.56 is a 50,000-60,000 psi pressure cartridge. I'm guessing that by the time the bullet makes its way down to the gas port, there is still 50,000+ psi of gas pressure running up the tube and one would think that would be enough to blow anything out!

I remember reading something on the internet that stated if you reload for your AR using H335 you'll have to clean your gas tube. I guess that's like most of the stuff I read....unsubstantiated garbage.

Gas port pressure is typically 15,000 to 30,000 psi depending on gas system length (assuming 556/223). It can be lower with some cartridges like 450 Bushmaster etc. But the small diameter gas port in the barrel creates a choked flow into the gas block/tube this limits pressure in the gas tube below gas port pressure in the barrel.

The gas tube itself ends up choking flow due to shock-wave propagation reflecting off the gas key.

The gas port size in the barrel is one of the best ways to control bolt velocity during cycling. But since this is hard for the end user to do adjustable gas blocks are the next best thing.

This all results in typical pressures inside the gas tube being somewhat lower than gas port pressure and then even lower in the bolt carrier group. The bolt carrier group typically being 2000-3500 psi again depending on gas system length.

Those number should be close it been awhile still I played with this.

mcb said:

The gas port size in the barrel is one of the best ways to control bolt velocity during cycling. But since this is hard for the end user to do adjustable gas blocks are the next best thing.

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When we built CAR's for the Recon detachment of the 7th, we hadn't figured that out yet, and cutting the issue M16A1 gas tubes down resulted in severe overgassing, so we carefully bent full-length gas tubes like pigtails to fit under the handguards of the CAR forends. It was a PITA, but it worked.

entropy said:

When we built CAR's for the Recon detachment of the 7th, we hadn't figured that out yet, and cutting the issue M16A1 gas tubes down resulted in severe overgassing, so we carefully bent full-length gas tubes like pigtails to fit under the handguards of the CAR forends. It was a PITA, but it worked.

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Saw some of those recently as a new manufactured item for AR's on some website looking for something else. Interesting to know that they actually worked.

The Swede 6.5 Ljungmann and used a curly que gas pipe and the Hakim used a wide space in the middle and had an adjustment to handle tube pressure …..anyone know what Colt did with the Aircrew survival weapon and SMG versions they made very early on?

Again I have certainly seen with my own eyes tubes full of crud from blank firing and personally tried to clear said crud with ball ammo firing....and the US Army that uses a lot more AR15s than anyone on here stocks and supplies to unit armorers long pipe cleaners specifically for cleaning those tubes

But do what makes you happy. I saw a bunch of those pipe cleaners at a Gunshow in Orlando this past week. Saw a lot of high prices on guns and ammo as well.

-kBob

mcb said:

...The gas tube itself ends up choking flow due to shock-wave propagation reflecting off the gas key...

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Negative, Ghost Rider. The velocity of the gas would have to be supersonic to create a shockwave. When a supersonic fluid passes through an orifice, its velocity drops to the speed of sound. Therefore, the velocity of the gas entering the gas tube is not supersonic.

kBob said:

and the US Army that uses a lot more AR15s than anyone on here stocks and supplies to unit armorers long pipe cleaners specifically for cleaning those tubes

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And they rarely get used, except maybe in Basic. I had some in my Armorer's kit, for display purposes. Used exactly one, to test the gas tube on my A1 right before I brought it to the shop to change the barrel after burning up thousands of M200 blanks after an FTX- yeah, it came out black, but the tube was wide open, no restriction. I had heated the barrel cherry-red to the point my roommate lit his cigarette off it.

MistWolf said:

Negative, Ghost Rider. The velocity of the gas would have to be supersonic to create a shockwave. When a supersonic fluid passes through an orifice, its velocity drops to the speed of sound. Therefore, the velocity of the gas entering the gas tube is not supersonic.

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Actually the gas is never super sonic while the bullet is in the barrel. Remember the speed of sound in a gas is dependent primarily on molecular mass and temperature. At the high pressures and temperatures in a gun barrel the speed of sound in those propellant gases can be as high as ~6000 fps. This is in fact a large part of what limits a gun powder propelled projectile's top velocity. It is extremely difficult to push a bullet faster than the speed of sound in the propellant gases. As you get close to the speed of sound in those gases the shock wave start to form and that chokes the gas flow in the barrel. This reduces base pressure on the projectile and it quits accelerating.

In the case of our gas tube the high pressure flow is choked at the gas port and expands into the gas tube that is initially at a much lower pressure/temperature and thus a much lower speed of sound. A shock wave can form at this gas interface and propagate down the gas tube reflecting off the gas key creating addition flow resistance in the gas tube.

Some references (a bit dated but still good light reading )
https://apps.dtic.mil/dtic/tr/fulltext/u2/704342.pdf
This paper talks about the shock wave in the gas tube.
https://apps.dtic.mil/dtic/tr/fulltext/u2/731218.pdf
This one has data from an instrumented M16 with pressure taps in the chamber, at the gas port, and in the bolt carrier. Somewhere in my archive I have a python coded simulation I wrote base on the models in this paper.

I wasn't sure if the gas in the bore was ever supersonic. I suspected it wasn't but had no data. But if it was, it'd slow to the speed of sound passing through the gas port.

I'll be checking out your links. I suspect they'll answer a lot of questions I have.