The longest sniper shot confirmed was 1.5 miles by British sniper Craig Harrison!

Craig Harrison is a Corporal of Horse in the Blues and Royals RHG/D of the British Army. He holds the record for the longest confirmed sniper kill in combat at 2,707 yards in 2009. The previous record was 2,657 yards by Rob Furlong in 2002. In November of 2009, Harrison killed two Taliban machine gunners consecutively south of Musa Qala, Afghanistan.

He shot at 2,707 yards, 1.5 miles, with an L115A3 Long Range Rifle. The weather was perfect for a sniper shot, but the low altitude of the valley helped, too. The rifle’s manufacturers said that the rifle is still fairly accurate beyond 1,640 yards, but luck would be needed to make a 2,707 yard shot. 

Harrison did it twice in a row, though. I think he’s just that good. Environmental conditions play a major role in bullet flight. The L115A3 long range rifle should technically only shoot 1,693 yards at the altitude of Musa Qala.