This twin-barreled shotgun’s barrels can be fired independently as separate attacks, or both can be fired at once as a standard action (the attack action).
A double shot that fires bullets is inaccurate, and takes a –4 penalty on both attacks. A double shot that fires bullets targets only a single creature and increases the damage of each barrel to 2d6 points (Small) or 2d8 points (Medium) for a total of 4d6 or 4d8 points.
A double-barreled shotgun uses metal cartridges (loaded with either a bullet or pellets) as ammunition.
Pathfinder Roleplaying Game Ultimate Combat. © 2011, Paizo Publishing, LLC; Authors: Jason Bulmahn, Tim Hitchcock, Colin McComb, Rob McCreary, Jason Nelson, Stephen Radney-MacFarland, Sean K Reynolds, Owen K.C. Stephens, and Russ Taylor.