The PKM, is the one and only machinegun ingame, only found in military loot spawns. the M4 deals 8000 damage/blood per shot, due to the rare ammo, this weapon is highly not recommended against zombies, the PKM is nice for close-med player encounters
2 HITS kill a player in most cases, but sometimes it may take more depending on the accuracy. so for suprise kills its recommended you unload 5 or more bullets on the victim.
The PKM uses PKM MAGS that are also extremley rare