The Elona+ version of the class adds the skills listed here in order to make the class "balanced" for consideration by the player. The standard Elona version only had Perception, Marksman, Firearm, and maybe Healing and Evasion, since they were meant to be only for throwaway NPCs that just attacked with guns.
The description is untranslated in game:
The gunner is a character who has mastered the use of firearms. His strong point is ranged combat using small arms. *[Barrage] grants a higher rate of fire.
In Elona+ There was added Class Feats, in which each class got a special bonus, the Gunner got:
|[Barrage]||Chance of an additional ranged attack||Can trigger even if the player does not already have a chance of an additional ranged attack from an item. (5%)|
|Warrior · Thief · Wizard · Farmer · Predator · Archer · Warmage · Tourist · Pianist · Gunner · Priest · Claymore|