I picked up one for my 9" 7.62x39 and another for my 14" 5.56. The one for the 9" seems to be a definite improvement. Recoil is much softer, though ejection was still erratic. Haven't tried the 14" 5.56 yet. I noticed that the ports are much larger and they seem to rely more heavily on the bleed port.
I had a really, really cool, detailed reply to some questions from one of HBI's engineers. I asked him about the possibility of a version without a bleed port, to eliminate the flash signature from the bleed port for night vision use, and he gave me a detailed reply indicating the extensive level of testing that lead up to the final design decision. He seemed to indicate that sticking with the bleed port offered two benefits: better drainage to prevent stoppages when the weapon is filled with water and a wider window of optimal operation per setting. Without the bleed port, it sounds like the gas settings have narrower windows for function.
I noticed that the packaging for my 9" gas cylinder was marked 7.62x39, 9" and 11". The 14" was marked 5.56 11" and 14".
