I was once at a sniper match competing with a bunch of long-range shooting specialists, some of whom had no problem making first-round hits at 1,200 yards. Then we encountered a stage where we had to shoot tennis balls hanging from strings about 15 yards downrange, that some of these shooters couldn’t believe they were missing.
Why? They didn’t know their come-ups.
When shooters take on targets within 20 yards, bullets will start to impact low, because the bullet path has not yet intersected with the line of sight of the optic. A rifle that’s sighted in to hit dead-on at long distance will shoot as much as 3 inches below the crosshair at 3 yards. That translates into a clean miss on targets such as the head box on a standard IPSC target.
The remedy is easy, and fun to do: Set up targets at distances of 3, 5, 10, 15, 20, and 25 yards. The targets should have a very small aiming point, such as a black dot. Aim directly at the dot, shoot, and take note of the distance between the bullet hole and the dot. Those will be your come-ups. Include that data on your range cards so you’ll always be ready for close-in shooting.
A riflescope is sighted in so that its crosshair intersects with a bullet’s path at a certain range, typically at 100 or 200 yards. At extreme close range, this can mean that the bullet will impact several inches below where you’re aiming.