How long would it take a 50 cal sniper to hit a target 1.5 miles away?

If the sniper was firing a standard 647gr full metal jacket projectile at a standard velocity of 2850 feet per second,and there is 5280 feet per mile.then we are looking at a distance of 7,920 ft. and a diminishing velocity as the distance grows.i would assume it would take a bullet flight of 6-8seconds for the bullet to travel this distance.