This musket has two parallel barrels; each barrel can be shot independently as separate attacks, or both can be fired at once as a standard action (the attack action).
If both barrels are fired at once, they must both target the same creature or object, and the gun becomes wildly inaccurate, taking a –4 penalty on each shot. Each barrel of a double-barreled musket uses either a bullet and a single dose of black powder or an alchemical cartridge 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.