Physics of Rifle Shooting Home Introduction Conservation of Momentum Conservation of Energy Bullet Drop Sighting in Bibliography Sighting In   In order to accurately hit a target with a rifle, you need a sight. A sight is a device which predicts point of impact of a projectile. In order to be effective, the line of sight of the sight needs to cross the parabolic path of the projectile. Most commonly the line of sight will cross the path twice due to the nature of the trajectory. When someone sights in a rifle they are simply changing the line of sight so that it crosses the trajectory at the desired distance. The path of a projectile in relation to the line of sight. http://en.wikipedia.org/wiki/Rifleman's_rule