Abstract
At rifle shooting, some adjustments on a riflescope, called “zeroing”, are required for precise aiming, and done with multiple trial fires. It is a matter of course that more trial shots make zeroing more correctly. However, no conventional data could be found to know how many trials make zeroing how accurately. There are some limits for firing a large amount of ammunition, to know the fact, causing not only budget but legal. Therefore, a distribution of bullet marks is analyzed at the setout, and it is ascertained that follows gauss distribution. Following simulations are based on that fact. Differences between bullet marks and the center of crosshair are normalized with their standard deviation to make relation free from shooter's skills, machining accuracies, and such shooting environments. Required numbers of trial shot are calculated to achieve arbitrary accuracies conclusively.
