I had my M16 with ciener conversion at the range today and ran another 800 or so rounds thru it.  I am around 8000 rounds on this unit now.  Today I only had ammo failures (2).  This unit seems to just get smoother.  I usually run Federal Bulk but we also tried Remington Subsonic today with a new SRT commanche suppressor.  It runs alot slower  with the subsonic  but function was perfect.  I still have the original recoil spring and firing pin which surprises me given what I have read here about firing pin failures.  At what point have you experienced failures?