Wednesday, July 25, 2012

Possible Gas Tube Issues With My AR

Well, my AR crapped out on me the other day.  I’ve had no issues shooting .22lr with the CMMG bolt conversion and probably put about 2000 rounds through it at the indoor range. No issues until I broke the CMMG bolt (It's still away on warrantee, see post here) The CMMG .22lr bolt was broken near the rear of the BCG, nowhere near the gas key.  So anyway, I haven’t shot any 5.56/.223 out of it for months, but I clean the gun pretty religiously (after every range night).  I even take the .22lr BCG out and store it in the container it came in, well oiled up.  What I neglected to do was to clean the gas tube by shooting 5.56/.223 out of it after shooting .22lr as recommended. 

Anyway, I've been itching to shoot my AR for a while since I broke the CMMG way back in early June so I took my Norc  up to PoCo outdoor range to shoot a little .223 Federal. It shot like a bolt action. The round would go out, however the bolt would stay in the forward position, spent casing not ejected. At first I thought maybe it was my extractor, but that wasn't the case because when I racked the charging handle, the spent casing came out no problems.  So I swapped bolts with my buddy and same thing, it just stayed forward. lug is dirty.

So I took it home detailed stripped the rifle, and gave all parts, including the stripped down BCG a good cleaning.  I’ll try cleaning the outside of the gas tube at the rear end a bit more, just to make sure there is a proper seal between that and the gas key.  

I even put some pipe cleaners that I got at Michaels through the gas tube.....there were no obstructions or anything, white colored pipe cleaner came out relatively clean. 

So my guess is there’s not enough gas coming out of the gas tube because I’ve gunked it up, or maybe I need to clean the gas key some more, or the bolt lugs need a more thurough, or there's a leak in the gas block, or maybe I just need to shoot some more .223 out of it.

I found a really good read here:

Cleaning inside M16/ AR 15 gas tubes

Folks, I don't often post on this forum as I'm one of the Instructors who help teach the Armalite Police Armorer's Course. I don't work directly for Armalite, but I am a contract worker for them for this and working AR's, M1 Garands, M14's, M1 Carbines, M 1903's and O3's and other military rifles at Camp Perry. Just want to make that clear before I begin.

OK, quite frankly I'm sick and tired of the CRAP that is put out on the open market about the many gizmo's for cleaning out the insides of gas tubes on AR's and M16's. Those very long pipe cleaners are nothing but an expensive waste of time. Other cleaning devices are even more useless. You do need to keep the outside of the gas tube clean at the rear end so it will form a good seal to the bolt carrier, but cleaning out the inside of the gas tube is virtually hopeless.

First of all, there is between 9,000 and 12,000 Pounds per Square Inch of gas pressure going through the gas tube depending on what length it is. That is going to blow out almost anything stuck or blocking the gas tube on one shot. However, it won't blow out stuck pieces of those long pipe cleaners and I wish I had a dollar for every gas tube I've replaced long before it needed to be done because a piece of those pipe cleaners was stuck in a gas tube.

What usually causes a gas tube to become unserviceable is wear in the area where the gas tube enters the bolt carrier key. When that happens, replace the gas tube as you can't fix it. The other thing that calls for replacement of the gas tube is when the gas tube has had so many rounds fired in the rifle that the tube clogs with carbon residue.

I don't believe anyone has solid figures on how often you should change a gas tube to keep optimum performance in an M16/AR rifle. From my experience, I would GUESS they are good for around 6,000 to 8,000 rounds at optimum performance, depending on how dirty the ammo is that you are using. Some foreign surplus ammo is real dirty and clogs the gas tube faster than G.I. or commercial ammo.

On real M16A1's and M16A2's I've worked on over the years, the gas tubes are usually good for the life of the barrel as long as they don't get worn in the area that goes into the bolt carrier key. On active duty, we replaced them more often for that than for crud inside the gas tubes.

What I recommend is that you have the correct spare gas tube AND gas tube pin for every barreled AR upper receiver you own. Then when the rifle becomes a bit sluggish, you put in the new gas tube and pin. Also, when you put a new barrel in your upper receiver - use a new gas tube and pin for it. Doesn't make sense to use a used gas tube with a new barrel.

Gas tubes aren't very expensive. The normally run under $ 20.00 and are cheap insurance to keep a spare on hand. You will spend much, MUCH more than that on the useless gimmicks to clean out the insides of them.

Anyway, I'll keep you posted....if anyone's reading this, haha!

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