I've just run an encounter for my players with several Carrionstorms. While doing so, one of my players with a weapon that did both Bludgeoning and Piercing damage (Akashic Mysteries' Hand Cannons veil, but a claw natural attack should have the same issue). Since a Carrionstorm is a Tiny Swarm, it takes 1/2 damage from piercing and slashing weapons, but full damage from bludgeoning. Does this attack deal full damage since it's bludgeoning, 1/2 damage because it's piercing, 3/4 from it being both bludgeoning and piercing, or something else?
I know that if this was just DR/Bludgeoning then the attack would overcome it fine and if the attack had wording like Flame Strike to split the damage between the two (or more) types, then it would do 3/4 (or whatever fraction) damage - assuming one type was bludgeoning and the other piercing.