[mvid]

Not sure, but I believe that they were using some proprietary system to account for wind/temp, because over that distance they will have a massive impact. Adjustments via drone likely just means they used a drone to get a better idea of adjustments for follow up shots. I would imagine that the rifle was even held by a device to make more precise micro adjustments

Assuming his rifle was factory accurate to 1/2 MOA and he made zero shooter related inconsistencies, and all environmental factors between the shooter and the target were accounted for, at 4km he would expect to hit inside of a 60cm diameter circle

Shots like this are mostly luck