The Machine Gun is a fully automatic rifle, it can fire 150 shots before breaking, and can be very useful against Special Forces who also carry it. It is visibly based on an M4A1 SOPMOD. The achievement "Perfect Gunner" is directly tied to this weapon, and requires the player to fire all 150 shots into a target without missing. A simple way to get this achievement is to go to the underground meat processing facility, aim the machine gun at a hanging slab of meat, and fire all 150 shots at it to recieve the achievement. Be careful with this, however, as a miss will be much worse than missing a shot in 72-hour mode. The survivor Brett Styles is best with a machine gun, as he can kill zombies with a great range and comes equiped with this gun.