A Predator MQ-1 has a service ceiling of 25,000 feet, a range of 675 nautical miles.
You’d need one hell of a shotgun to take that out. The AGM-114 Hellfire has a range of about 5 miles, and travels at Mach 1.3. 20 pound high-explosive warhead.
You’re gonna need a bigger shotgun.
It would probably be more plausible to jam UAV’s using ‘spark gap’ methods.
1 ga.!