Heavy gunners carry heavy machine guns that fire in a wide arc and they carry a large ammo box behind their backs. Their weapons have higher accuracy and damage but lower range and ammo capacity compare to Gunner Elites' light machine guns. Also, their bullets can even penetrate Armored Tech's shields, albeit dealing reduced damage.
Like other gunner classes, during interception or support fire, heavy gunners fire in a straight line instead of sweeping across. Therefore, given their weapons' high ammo capacity, they deal massive damage to infantry units and in most cases, no infantry can ever go past them. One strategy versus bosses is to place gunners behind bosses so they can assist another unit as support fire.
The main roles of heavy gunner and other gunner classes are camp defense and intercepting enemies. However, if used correctly, they can be powerful assault units. When attacking, it is best to position them as close to the target(s) as possible and try to aim where as many bullets can hit as possible, i.e. shoulder to shoulder. Aiming at the head might not be a good idea since heavily armored units can take a bullet or two in the head.
Compare to Gunner Elites, heavy gunners have lower AP, therefore they are not as useful in offensive role.
Gallian Heavy Gunners
Heavy gunners did not appear in Valkyria Chronicles.
Valkyria Chronicles 2
Valkyria Chronicles 3
Heavy gunners no longer exist in Valkyria Chronicles 3. However, heavy machine guns are still available for purchase and can be used by the gunner class. However, unlike in VCII, the VCIII 'heavy' machineguns are not the most powerful, but at F-levels they boast accuracy in the high 90's.
GRA Heavy Gunners
Their role and equipment are the same as their Gallian counterparts.