Hans beat me to it. If the trajectory was flat and the bullet maintained its muzzle velocity over the distance, the time in flight would be 3.75 sec. The article was clear about the trajectory, the need for the shooter to "hold over," so it doesn't take a rocket surgeon to understand the longer flight time.
It must have been difficult to see the impact points of the sighting shots, so there must have been a lot of "
Kentucky Ottawa windage" involved in making the shot. Translation: Skill.