I'm betting that you're seeing the same thing discussed above -- that on buffs you're geting fuselage hits (maybe with displaced hit sprites). With the smaller "hit boxes" in AH2 its easy to stay just below the kill threshold at several nearby damage centers...
Try going offline, and hit the drone 24s with 30mm only -- targeting out from the fuselage, so there's no doubt. 30s have plenty of damage power....