I notice that people don't shoot the zombies on their head but instead they shoot below the head, they want to get more points but they are loosing ammo and don't survive at all. Shoot on the head so that you won't run out of ammo. Only do this when a swarm of zombies if in yous ass. Check all sides before turning around. if you see a zombie in front kill it then turn around to shoot their heads of. This way you don't die as fast... Tell me if it work or not...