A reply to this ancient thread...
Long ago, at a place known as "Ft Bragg", Pv2 Snuffy (possibly could have been me
) wanted to impress his Squad Leader with the cleanest M-16 EVER
. So the upper minus hand-guards and BCG goes into the dry solvent tank in the motor pool. Never figured out how a liquid solvent was "dry"...
Let it soak a while with some occasional stirring around. While waiting on the soak, it occurs to Snuffy "Hey! I bet I can use the air hose off the compressor (for filling tires) to clear the gas tube out". Very carefully the end fitting of the hose was inserted into the upper receiver chamber and a good shot of air was delivered. Presto! A jet of solvent and solvent mist comes out of the gas tube... straight into my face.
You know those safety goggles that hang by the solvent tank/tray? They work well for the eyes, but not so much for the mouth and nose. Just so you know.
That gas tube was absolutely clean and clear.
PS: In 37 years of using/shooting these things, I have never heard of an AR gas tube getting so dirty it failed to work.