General Discussion
In reply to the discussion: British SAS sniper kills ISIS flamethrower executioner with a crack shot to save 12 hostages [View all]muriel_volestrangler
(101,316 posts)hitting a building.
In 5 seconds, a bullet (or anything) will drop about 125m if fired horizontally - s=ut+at*t/2 .u=0, a=10m/s/s.
If the OP story is real, then he was nearly a mile (1603m) away - call it 1500m. 5 seconds would be a quite a slow bullet - 300m/s, or just below the speed of sound. I'd expect a sniper rifle to be faster than that - Wikipedia says it's 852m/s.
So say it takes 2 seconds to travel the distance. If you want to aim a bullet, then ignoring air resistance, the top of the arc should be reached after 1 second - which means it needs 10m/s vertical velocity at the start. So he'd need to aim about 10m higher at half the distance, or 20m above the target at the full distance.
Well, I supposed that means the sights have to be set for 20m difference. I guess with laser range finding to give you an accurate distance, it can be attempted. You'd need to know the wind very well to do it with the first shot.