I'm not sure what type of ammo is being shot at you but a cannon shell could still have lethal velocity (and damage potential) at 450meters (=1500 feet)...
I wonder why he stated distance in feet? You mean yards, perhaps?
Effective Range of a Cal.50HMG is stated with 1800-2000m. That is up to 6000ft and 2200 yards. AFAIK the range of an MG131 is roughly the same.