Your understanding of Gun Arms allows you to swing and fire your gun arm at the same time.
Prerequisite(s): Exotic Weapon Proficiency (Gun Arms).
When you use the full-attack action, you may fire your gun arm as an additional attack against the same target if you have successfully hit with a melee attack using the gun arm during the round, using the same BAB with a -5 penalty without provoking attacks of opportunity. You may only use this feat once a round.
Normal: Without this feat, you can’t fire the gun arm at the same time as you swing your sword.