Factual error: In the opening sequence, the range for the shot is confirmed as 650 yards. Moments before the shot, AFTER he had his target centered in his scope, Berenger swings the muzzle of the rifle at least 10 degrees. At 650 yards a change of only a single degree in the angle of the muzzle to the target would mean that the target would have to move 11.34 yards laterally in order for the shot to hit. If Berenger actually had to swing his rifle ten degrees in the span of a second in order to keep his target in view, that would mean the target was sprinting at a speed of 340.32 feet per second, or about 232 miles per hour, and had covered 113.44 yards during that time. Absolutely impossible.
Trivia: The movie Sniper is actually a factual story loosely based on the biography of a United States Marine Corp Sgt. Carlos Hathcock. Sgt. Hathcock was a sniper during the Vietnam war. A book called "Marine Sniper" written by Charles Henderson has the same stories where Tom Beringer crawls across the field to get into range to shoot the drug lord and also where Berenger is stalked by the enemy sniper where he shoots him the other sniper and the bullet goes through the rifle scope. Those two scenes actually happened in real life.