The Mercenary Gunner can change between walking stance and prone stance. When prone, the Gunner will receive a damage resistance boost and fire his machine gun without interruption as opposed to the bursts he would fire when standing.
When ordered to go prone, the Gunner retains his ability to move, albeit at a slow crawling pace, so altering back to walking stance is advised when it comes to taking the fight forward.
Stands up and uses the assault rifle.
Goes prone and uses the machine gun. While using the machine gun the Mercenary Gunner can fire without having to reload and becomes more resistant to attacks but moves slower.