Goose gun
Back in the 19th century, American market hunters employed large gauge (8 gauge or 10 gauge) shotguns with full choke and long barrels to knock high-flying geese out of the sky from their migratory formations. These heavy shotguns threw larger lead shot in a tight pattern at considerably longer range than the normal 12 gauge shotguns used for ducks and other smaller fowl.
Of course, this might lead to goose-gun armed tower guards following their target downward toward the prisoners shoving and pushing and milling about to be first to grab the goods, which could lead to unintended (?) wounding. Then again, such a threat might discourage the prison population from taking delivery. And it's not like America has a shortage of prisoners. They're expendable.
Marlin Arms Co. made and sold goose guns of a bolt-action variety until the mid-1960s. Perhaps they could be persuaded to make a production run for the Federal anti-drone troops.
Biting the hand that feeds IT
