There's a very big difference between the maximum distance an individual pellet of birdshot will go (which is still likely less than 300 yards at its maximal ballistic trajectory)and the "effective range" which is usually defined something like 'the maximum range at which accurate fire will produce a 50% hit probability'.
For birdshot, that's usually considered to be around 40 yards for a bird. A drone would probably be similar.
For birdshot, that's usually considered to be around 40 yards for a bird. A drone would probably be similar.