Twinned Barrel

A Twinned Barrel weapon has two barrels that can each hold a firearm bullet and can both be loaded as part of reloading the weapon. You can fire both barrels of a Twinned Barrel weapon as part of an attack, instead of each barrel individually. Doing so empties both barrels of the weapon (as per the Barrel property) but increases the damage die of the weapon on a hit (from d4 to d6 to d8 to d10 to d12).