Replaces the firing sounds of the M4A1 with those from Counter-Strike: Source. Since it also affects the "Para SMG", I've replaced its akimbo sounds as well.
You will hear SWATs and FBIs using it on lower difficulties, Medics and Tasers have M4s on all difficulties, plus the AK used by Russian mercs (and Sosa's guards) use the M4 sound for some reason (in addition, the Russian Medic has an actual M4). The Russian mobsters in Hotline Miami have the true AKs instead.