FWIW- Two Royal Marines snipers killed a pair of Iraqis in 1993. The snipers were at a range of 860 meters and dropped the pair simultaneously. The wind was moving so briskly that their windage adjustment was 56 feet to the left.
Carlos Hathcock, the famed USMC sniper, took a NVA captain at a range of 2250 meters. He got 92 others at varying ranges. The longest shot to date is by Canadian sniper Rob Furlong in Afghanistan at a range of 2,430 meters.