Norwegian Kongsberg Defence & Aerospace has has signed a contract with Germany to deliver a Counter Unmanned Aerial System (C-UAS) based on the
PROTECTOR Remote Weapon Station, value 27,4 million dollars.
40mm programmable ammunition.
EASA (EU) has specified minimum 20 meters (65 feet) over private property, and that seems reasonable to me.
https://www.easa.europa.eu/sites/default/files/dfu/217307_EASA_DRONE_POSTER_2018%20final.pdf