> Laser systems would be completely unrealistic for this situation
Rheinmetall has sold Laser systems to protect venues at the Olympics, World Cup and other large events for several years now – and their systems are used by several militaries on their bases and in the field for the same purpose.
The problem with a shotgun is proximity. The effective range of most common shotguns (12 or 20 guage) is a lot closer than most people want to be to anything explosive that is on a trajectory towards you!
Seems like an air burst scatter shot weapon would be more effective. Something like a shotgun with explosive projectiles. Use the concussive blow to cause damage.
What goes up must come down gaining velocity in the process. This is exceedingly dangerous. Google for deaths from guns fired in the air at marriage parties / celebrations.
Rheinmetall has sold Laser systems to protect venues at the Olympics, World Cup and other large events for several years now – and their systems are used by several militaries on their bases and in the field for the same purpose.