How do you k is “t” prior to shooting? I know you can range the target but it seems to me that determining t could be a challenge.
Ff you know your muzzle velocity and distance you can compute time. The physics involved in a 1.5 mile shot is simple math. The physics involved in making that math apply in the real world is really complicated. Wind, elevation, humidity,and after all that your target has 3 seconds to just move. Amazing shot.
I’m no expert but bullet speed in a vacuum is very accurately known for a given weapon. Atmosphere slows it down. Dust and humidity affect the speed and therefore the duration of the flight.
My simple calculation was intended to estimate the large elevation compensation required to actually hit the target. In fact the actual compensations are much more complex. As an earlier poster noted this shot is more like a mortar than a bullet.