was the range target zone 350,000 square feet? Did they also have the barrel end pistol grip? You may have also missed that the JP4 tanks 1100 feet away also have bullet impacts.
Have you ever fired a machine gun or bump fire rifle? People who have never fired a machine gun think that all you have to do is point it in the general direction and mass killing will happen. At 400 yards a slight movement in the barrel will throw the shots off by yards at the target area ... generally shooting high and punching holes in the sky.