Put my m4-2000 on and really like it. Was an easy install and took only an ajustable wrench and a hand drill. The whole process took maybe 10min. Yeh the halo is nice to use on a nato flash hider but the M4-2000 mount is nice and quick. I would also bet that the action noise is what you are hearing and making them sound alike. Both the action noise and the sonic crack totally hide the muzzle report with mine. Sound readings alone I am sure the AAC can is quieter, certainly the new one.