In 2017, a Canadian sniper team took down an ISIS fighter from a distance of 3,871 yards, over two miles. Record-breaking by over a thousand yards, the seemingly impossible shot was accomplished. Set up on top of a building and using a McMillan TAC-50 .50 sniper rifle, the bullet took ten seconds to reach the target. This feat was accomplished by the incredible math skills the sniper pair had perfected. Wind speed, gravity, humidity, and barometric pressure all have an effect on the bullet as it travels through the air. The team must be able to measure these factors, know and understand how they affect the flight path, and then calculate the corrections needed to hit the target.
Source: https://nationalinterest.org/blog/buzz/3871-yards-how-sniper-got-worlds-distance-kill-record