Enhanced/Heavy Duty Gas Tubes

**Moltke** · 01-09-12, 16:11

Seems like a gimmick to me.

**az doug** · 01-10-12, 00:38

Take a look at the Colt/Diemaco LMG (modified M-16). It used a gas tube with thicker tube walls for sustained full auto fire. It also used a hydraulic buffer lower the cyclic rate.

**armatac** · 01-11-12, 14:49

You mean this...

This is a standard inside diameter but .25 od straight tube, the same as the current LSW tube. I think the weak spring and heavy buffer was not the greatest components to add to the system but when it had the open bolt it was probably done to minimize the beating on the hammer that held the bolt carrier to the rear as the open bolt machine gun.

So this is standard stainless tubing turned down on the ends. The inconel is only needed if you need to keep the tube the current size. If you have the room you just go with oversized stainless. Note..the LMG upper also supports the gas tube where the handle is to prevent from drooping. I swear you can probably extend the life of a tube a significant amount if it were not stressed by its own weight and movement when red hot.

I have the specs on this tube on my old computer. If you're doing a tube for the AR you need to make a little bending jig with pins where the bends would be, be careful to not pinch at the bends. Make sure you get the end going into the carrier just like the standard to within .0005" of od on the head.

It's odd that the AR has rings on the bolt body, not on the small tip, and ofcourse it would be hard to have a ring on the tube. If these would have been incorporated dimensional tolerances could be much more lose and performance would be less determined on the tolerances of the output product. Its actjually amazing we have been able to nail all the manufacturing steps necessary.

**Moltke** · 01-11-12, 16:07

What is the life of a gas tube?

How much would go into the development of this part as opposed to just buying a new one for .... almost nothing?

**bfayer** · 01-11-12, 16:09

I would be concerned about shifting the failure point to something that would be more expensive to repair, and has a greater risk of causing bodily harm when it fails.

**TacMedic556** · 01-11-12, 16:11

Originally Posted by MK18Pilot

Where can the video you are referring to be found?

Videos in article: http://atwar.blogs.nytimes.com/2010/...and-m4a1-guns/

Great article on COLT M4: http://atwar.blogs.nytimes.com/2010/...standard-arms/

Another article: http://atwar.blogs.nytimes.com/2010/...e-reliability/

**TacMedic556** · 01-11-12, 16:14

Couple points that are relevant:

Marines carry what 210 rounds (7 mags) in a loadout? It took far more than that to make it fail.

Perhaps no person would ever be in a situation where they fired this many rounds, and able to reload this quickly.

Shooting an M4 in combat, in schools, at range and for fun, the gas tube will not fail for a long, long time.

**armatac** · 01-11-12, 17:21

The fires downrange were from the other weapons at knob creek.

The failure point is what it is, my point is education, it isn't a particular round count. Did you see how long I actually took between mag changes? I can nuke them lots faster. The point I was trying to make was that it is dependent on the firing discipline. The video showing the Colt test is not a measure of the amount of rounds it takes to kill a tube, do you see the amount of time it is taking for the magazine change. Well if you are faster or slower than that guy then your failure point is different. This is the most true thing I have ever said.

So you trained real hard and you're a ninja mag changer, well given the same firing rate as your buddy because of the time difference you have a different gas tube failure point and cook-off point.

If you have a weapon that is to be used in an environment where there is a possibility of someone totally dogging out the weapon to survive, they are going to do things that are different than your average range day. There have not been reported issues of tubes failing causing problems. I have seen some questionable reports about failing M4 in heavy combat that are plagued with interesting data and wonder if the failure modes were ever attributed to gas tube failures.

of all my torture I think in the end the gas tube is pretty good the way it is, if you have full auto I would look at something that would provide a small help. That is why I suggested the support like seen on LSW. A stupid little block about 1/4" tall of whatever would support the underside of the tube during glowing sagging and isn't that revolutionary. The defense of it being a "fuse" for the system I just don't get because when it goes down it goes down, there is no quick fuse change to get it back into action. Also, I mentioned I had tubes bust just after repeat thermal cycles.

http://img513.imageshack.us/img513/4113/tube001.jpg

here is a pic of some of the tubes that were made, I had a pic somewhere of all the tube failures, generally they look the same with the same sag point.