This is the schtick to make area attacks with Guns.
You have some special technique that lets you make area attacks with normal guns. This could be sticks of dynamite tied to arrows, special homemade explosive rounds for your shotgun, hosing down an area with gobs of auto fire or just a magical ability to cause your missiles to explode in a fantasy cosm. However you do it, you first spend an extra shot preparing before making such an attack. You then make the attack, which now affects an area with a diameter equal to the damage value of your weapon. Use normal Area rules. Not cumulative with CarnivalOfCarnage, CleanShot, EagleEye, or HailOfBullets.
This schtick might not be appropriate for all periods and weapons, and can require some special equipment, stuff that you can get your hands on fairly easily. The fantasy variant (fireball arrows) costs a Magic Point instead of an extra shot. It all depends on how you do it.