In the temporary duty scenario or eden editor enter a zpu quad 14.5mm or m56 quad .50 (including vehicle mounts), as the gunner, aim at the ground or at a nearby object and fire while observing the bullet impacts. Notice each time the weapon is fired projectiles alternate between hitting 4 points on the object/ground while the particle effects and shell casings suggest all 4 barrels are firing at the same time. Either make all 4 barrels fire at once or adjust the ammunition consumption & effects to match the projectiles coming out of the gun - the former seems more appropriate considering the nature of the weapon systems.

EDIT: After testing it seems that the m56 does considerably more damage against vehicles than a single .50 so i guess this was a design decision around making the quad mounts good against vehicles/aircraft and nerfing them against infantry? I expected the m56 to just be 4x .50 cals but it appears to be much more than that