Instructions
Sight your rifle in at 200 yards. Once your rifle is sighted at 200 yards, become very familiar with how your rifle shoots at 300 and 400 yards, noting specifically how far the bullet drops at both distances. Each caliber will be different. Some rifle calibers shoot flatter than others, like the 7 mm Magnum, so they will drop less than other calibers. Familiarity with your firearm is very important.
Divide the amount of bullet drop at both distances in half when shooting up or down at a 45-degree angle. This is a good estimate to judge the amount of drop the bullet will experience at that angle (45 degrees is half of 90 degrees or half of a horizontal shot).
Estimate the amount of drop a little higher for angles between 45 and 90 degrees, and lower for angles between 0 and 45 degrees.
Purchase a range finder or rifle scope with a feature called angle range compensation (ARC). This feature takes the angle of the shot into account when recommending how the shooter should take the shot. The range finder or rifle scope will display the distance of the shot, the angle of the shot and the distance at which you should treat the shot. For example, the distance of the shot may be 384 yards, the angle may be 35 degrees and the range finder or rifle scope will tell you to treat the shot as a 325-yard shot, so you will shoot a little lower.