JBM - Calculations - Ballistic Coefficient (Time) Terms

Input Data

Altitude

Used in estimating the atmospheric conditions. This value is not used unless the Standard Conditions at Altitude checkbox is checked.

Distance

The distance over which the time is measured. For a setup of a chronograph and timer, the distance is measured from the center of the chronograph (start of time) to the second timer detector which turns off the timer.

Corrected Pressure

Check this box if the pressure entered is a corrected station pressure. If it is an absolute pressure, leave this unchecked.

Drag function

A drag function (or G function) provides the forces on a standard bullet for which the drag function was derived. A bullet's ballistic coefficient then relates the drag on any bullet to that of the standard bullet.

Near Velocity

The velocity of the bullet at the beginning of the measured distance.

Pressure

The barometric pressure. It may be corrected or uncorrected depending on the state of the "Corrected Pressure" checkbox.

Relative Humidity

Relative humidity (percent)

Standard Conditions at Altitude

When checked, the temperature, pressure and humidity for standard atmospheric conditions at the entered altitude (always 0% at standard conditions) are entered in the calculation. The standard used is the ICAO standard atmosphere.

Temperature

The measured or estimated air temperature.

Time

The measured time of flight of the bullet over the entered distance. This value needs to be entered to an accuracy of a microsecond.

Output Data

Ballistic Coefficient

The calculated ballistic coefficient for the selected drag function.

Atmospheric Density

The calculated density of the air.

Far Velocity

The calculated velocity at the end of the measured distance.

Speed of Sound

The calculated speed of sound.