You know you wont get blasted if you hit those casks from the rafters above the adjoining room FYI. But for me at least I want the powder intact to use for later, so I snipe the ones inside or go in and steal it all earlier when the room is empty and NPC's are outside guarding the room from front and I drop down in from behind the door through crack in wall without them seeing it. So yeah, I don't think the "Leroy Jenkins" path is the right one for this encounter.