The machine gun is a fully automatic rifle capable of firing 150 shots before running out of ammunition. It is carried by Special Forces members, and is dropped upon their deaths. It is visibly based on an M4A1 SOPMOD with an MP5A3's stock in Dead Rising and an M4 Carbine in Dead Rising 2.
The achievementPerfect 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 receive the achievement. Be careful with this, however, as a miss will require you to repeat the process.
The survivorBrett Styles is the only survivor who comes equipped with a machinegun.
During Infinite Mode, the Machinegun can be found in the warehouse of Colby's Movieland after beating Sean Keanan when he is in the theater area.
It should be noted that the Machinegun has a Grenade Launcher attachment, although none of the SF Soldiers are seen using this attachment nor this option is used in game.