Ballistic coefficients can be found in reloading manuals, but they can also be calculated from two velocities and the range between them.

Before calculating a bullet's ballistic coefficient, enter the altitude, temperature, pressure, humidity, wind direction, and wind speed that existed when the velocity data was acquired. This allows Ballistic Explorer to correct the ballistic coefficient to standard sea level conditions. If you don't know what the conditions were, use the standard values.