Actions

Machine Gun. The gunner fires their machine gun, consuming 10 rounds of ammo. All creatures in a 240 ft. line must succeed a DC 15 Dex save or take 11 (2d8+2) piercing damage. Creatures further than 80 ft. have advantage on this save. Ammunition, Two Handed, Reload (50)
Creatures in the line must also succeed a DC 15 Wis save or become suppressed until the end of their next turn. A suppressed creature has its movement speed halved, can only take an action or a bonus action on their turn and can't concentrate on spells.
Shortsword. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d6+2) piercing damage.
Smoke Grenade. The gunner throws a smoke grenade up to 60 ft. One round after it lands, the grenade emits a cloud of smoke that creates a heavily obscured area in a 20 ft. radius. A moderate wind (10-20 mph) disperses the cloud in four rounds, a strong wind (>20 mph) disperses it in one round. The guard can use this ability twice before having to restock.

Bonus Actions

Mount Bipod. The gunner uses the machine gun's bipod to mount the weapon on a surface. The weapon can not be fired while it is not mounted. The gunner is immobile while the weapon is mounted. Dismounting takes 10ft of movement.