My own M4 went over 7,000 rounds without cleaning, and the Danish trials of the Canadian C7 (a modern M16A1 with some A2 features) went over 15,000 rounds before a failure.

I just don't understand why people have such a problem with the direct gas-impingment system.  It has worked well for over 40 years, and has seen hard use in many wars and conflicts during that time.  If the current system didn't work (and work well), it would have been changed, or the rifle scrapped and replaced, long, long ago.  Instead, countries are dumping rifles they built themselves and are buying AR-based rifles, because they've proven to be the best design out there.

If you want a gas pistol rifle, why not buy one designed that way?  Modifications to an AR will give you a compromised gun, which is why all previous attempts have failed.

-Troy