I just got my first kac gun, a 16" mod 2 and absolutely love the thing. Only thing I changed on it was putting a surefire warcomp on so I could try a friends suppressor while waiting on my form 4 to get approved. Also put a geissele airborne charging handle in since I got one on the labor day sale for cheap.
When not using a can the gun is about the smoothest shooting rifle I've ever shot.
Put my friends surefire can on it and after 4 or 5 shots we both had to stop shooting it because of the amount of gas back in the face.
I expected more back pressure from the can but not that much. We let the can cool down and took it off and put it on his geissele urg-i and had no problems with gas in the face.
Could it be because of the mod 2 gas system? Super tight seal causing the extra gas in the face?
Other than this I'm in love with the rifle and its quickly become my favorite 16" I've ever shot.