The stock heavy gun is a custom machine gun with the bolt located on top of the receiver. It is loaded with drum magazines attached to the left hand side of the weapon. It uses a stock from a Para Minimi and its grip and whole front half are based on the M60E4. There is no ejection port on the weapon.
The parts that are based on the M60E4 are actually recycled from an earlier heavy weapon model that was briefly present in earlier stage of Mad Paintball 2 alpha.