Except there are no silencers for an AK. They are suppressors meant to hide the muzzle flash. It will dampen the sound but it will still be audible at a distance. I am aware you can use subsonic rounds but they cycle like poo.
2300 hours and I finally turned it off as well. It was more interesting when they attacked random spots on the wall. It got to the point of figuring out the easiest cheese method. Now I just play with max zombies and some mods.