Solving fire control problems using ballastic trajectories is as old as the cannon itself. For any projectile weapon on a horizontal firing plane, max distance is achieved with the barrel at an elevation of 45 degrees. Anything above or below this will reduce the range. This is Physics 101. Indirect fire weapons (elevations above 45 degrees) are more accurate because if they are off target a little bit, they will hit closer than one firing right at it that will go shooting past.