You can double top for extra damage, but how about wailing away with those extra cartrages into the body!
Put more rounds center mass means that center mass hurts more!
Benefit(s): Any time you use a weapon that allows you to fire multiple times before a reaload, you may spend one additional round or charge to add an additional die of damage to the damage upon a hit. As an example if a weapon does 1d4, this feat would allow you to do 2d4. If your weapon would do 5d4, you would do 6d4. You can do this as part of a burst, automatic, and full attack action, but you must choose to do so before you roll your attack.