Army Spy Blimp Tested Over New Jersey

No. You 50 cal has a max range over horizontal ground of 7.5 km, max (4.68 mi). That's not aimed, just how far the bullet would travel over level ground if you aimed the gun at a 45 degree angel, for max distance, and pulled the trigger. It would be far less if you aimed it up, of course. While the blimp might only be a few miles overhead for training (still higher than your 50 cal could reach), during actual use (and the last time I saw it in training) it was a lot of miles in the air (that's a technical term).