A free app for Android, by Peste Razor.
This app is a very useful ballistics calculator for rifles and guns, as well as other optics. It is based on the ballistics calculation method of the MOA (Minute of Angle). This is the most accurate method for calculating the ballistics of a shot.
The app allows you to set the target distance, the inclination of the rifle, and the scope. It also allows you to use the blowgun, pistol, bow, or any other weapon.
The basic instructions for a ballistics calibration are:
Once you have shot with the weapon, use the scope to measure the distance between the center of the target and the hole on both the vertical and horizontal axis (the difference in height and width).
If you have shot with the rifle, use the metal ring on your optics to adjust the next shot by one or more "clicks" on both the vertical and horizontal axis. The value of each "click" is a fraction of the MOA (Minute of Angle) calculated by the app.
MOA Calculator is a very lightweight and simple ballistics calculator.