I have no training in the physics of ballistics but I imagine the effective range of a shotgun is enhanced considerably if it is shooting down from above. Accelerating 00 buck to muzzle velocity and then allowing gravity to assist could allow the drones to fly completely out of return fire range and still pose an effective threat. But what do I know?
I imagine the ability of a drone to stealthily creep up to your bedroom window and blow your head off while you sleep gives it a bit of an advantage.
Demo video:
http://www.youtube.com/watch?v=Ffem5Kejhso