- Altitudes
- A comma separated list of altitudes. These altitudes
are used to calculate the standard density at the entered altitude. You should
enter altitude densities (in feet or meters) here. It is important to understand
that this is the
*only*value used to find the density of the atmosphere. The program assumes that whatever instrument provides the density altitude measurement takes into account all necessary variables. Temperature is not used to calculate the density since it is already taken into account in the density altitude. See Density altitude for more information. - Ballistic Coefficient
- The ballistic coefficient for the bullet being used. It is almost always obtained from the manufacturer, but can also be measured. The ballistic coefficient is represents the ratio of the drag of the standard (e.g. G1 standard bullet) bullet to that of the bullet you are shooting. A ballistic coefficient of 0.100 means that your bullet has 10 times the drag of the standard bullet.
- Bullet Length
- The length of the bullet. When using a bullet in the library, this value is only used if the library value for length is zero (unknown).
- Bullet Library
- A drop down list showing all the buttons in the library. If a bullet is selected, the trajectory is run with the selected bullet. If "None" is selected, the entered BC, drag function and weight are used. Lapua bullets with "(CD)" in the description use the Drag Coefficients supplied by Lapua instead of the ballistic coefficient. Bullets with "(Litz)" in the description use Bryan Litz' BCs.
- Bullet Weight
- The weight of the bullet.
- Caliber
- The diameter of the bullet. This value is not used by the calculation, but is printed on output.
- Cant Angle
- The angle of the tilt of the firearm to the right or left from
vertical. Positive angles are to the right. This value is
*not*used for the zero trajectory. It is assumed that the zero conditions are flat with zero line of sight angle and zero cant. - Distance to Chronograph
- The distance from the firearm to the chronograph (typically midpoint) at which the velocities were measured. This value must be the same for both the high and low velocities.
- 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.
- Drop Units
- The units for drop outputs. For units of MOA, enter "1.0" and select "MOA" for the units. To match a scope turret unit, enter the value and units. For example, a scope that has click units of 1/4 MOA, enter "0.25" and select "MOA" for the units.
- Include Only Notes in Header
- If checked, only the "Notes" are displayed at the top of the output. All other inputs are not printed in the header. This makes the output more compact.
- Include Spin Drift
- If checked, the Litz spin drift is calculated for each range. The bullet length must be entered (even if you are using a bullet in the library) to calculate spin drift.
- Line of Sight Angle
- The angle between the line of sight and level ground. This value
is used when shooting uphill or downhill. Value is a positive angle when shooting uphill
and a negative angle when shooting downhill. This value is
*not*used for the zero trajectory. It is assumed that the zero conditions are flat with zero line of sight angle and zero cant. - Low Velocity
- The muzzle velocity measured at a low temperature. If you know the muzzle velocity for only one temperature, you may enter the same value for the low and high velocities and low and high temperatures. The program will not perform any temperature correction for muzzle velocity. NOTE: I have simulated a low temperature (32 °F) shot by cooling bullets in and ice water bath (in a sealed bag!).
- Low Temperature
- The temperature at which the "Low Velocity" (above) was measured.
- High Velocity
- The muzzle velocity measured at a high temperature.
- High Temperature
- The temperature at which the "High Velocity" (above) was measured.
- Notes
- Text displayed at the top of the card. Typically used for firearm description.
- Ranges
- A comma separated list of ranges. The output includes a bullet drop and windage for each temperature, altitude combination at each range. Units of ranges are the same as for the zero range.
- Round Output to Whole Numbers
- Removes any part of the drop, windage or lead after the decimal point. This is useful when your drops match the scope click settings and you want the output to be in number of clicks.
- Sight Height
- The height of the sight (or scope) above or below from the centerline of the barrel. This is required because the bullet starts at a drop of -[Sight Height].
- Sight Offset
- The offset of the sight (or scope) to the left or right of the centerline of the barrel.
- Show Drop and Windage Deltas
- If checked, only the differences in drop and windage from the zeroed trajectory are printed on output. Differences are in units of "Drop Units" and "Windage Units". This option is most useful when you know the bullet drop and windage for your load at some condition and you want a table of corrections.
- Target Relative Drops
- Calculates the bullet drop relative to the target and not the line of sight. These values are only different when the cant angle is non-zero.
- Temperatures
- A list of temperatures used to calculate a muzzle velocity for output. This input is also used to calculate the speed of sound to find the value of the drag function. This input is not used to calculate density. Output includes a drop and windage for each temperature-altitude combination.
- Windage Correction for Zero Range
- If checked, the windage is changed to make the bullet cross the line of sight at the zero range -- zero windage at the zero range.
- Windage Units
- Same as for Drop Units, but for the windage values.
- Wind Speed
- The speed of the wind.
- Wind Angle
- The angle of the wind relative to downrange (0 degrees), 90 degrees is to the shooter's right, 180 is a head wind, and 270 degrees is to the shooter's left.
- Zero Altitude
- The altitude at which the firearm was zeroed. This value is used to find the atmospheric density.
- Zero Height
- The height of the zero point at the zero range.
- Zero Offset
- The offset of the bullet impact to the left (negative) or right (positive) of the target center at the zero conditions.
- Zero Range
- The range at which you wish the bullet to cross the line of sight. The units selected for the zero range are also applied to the "Ranges" value.
- Zero Temperature
- The temperature at which the firearm was zeroed. This value is used to find the muzzle velocity using linear interpolation between the high and low velocities. It is also used to find the mach number for interpolation into drag tables.
- Zero Wind Speed
- Wind speed at time of zero.
- ZeroWind Angle
- The angle of the zero wind relative to downrange (0 degrees), 90 degrees is to the shooter's right, 180 is a head wind, and 270 degrees is to the shooter's left.

- Ballistic Coefficient
- The entered ballistic coefficient
- Bullet Weight
- The entered bullet weight
- Caliber
- The entered bullet diameter
- Cant Angle
- Entered cant angle
- Drop Units
- Units used for bullet drop
- Line of Sight Angle
- Entered line of sight angle
- Show Drop and Windage Deltas
- If "Yes", the table shows the drop and windage differences from zero range. If "No", actual drop and windage values are shown.
- Sight Height
- Entered sight height
- Sight Offset
- Entered sight offset
- Windage Correction for Zero Range
- If "Yes", the table was calculated with the correct windage angle to make the windage value zero at the entered zero range. If "No", then windage was not corrected.
- Wind Angle
- Entered wind angle
- Wind Speed
- Entered wind speed
- Windage Units
- Units used for bullet windage
- Zero Altitude
- The entered zero conditions altitude. This value was used to calculate the density at zero.
- Zero Height
- The entered zero height.
- Zero Offset
- The entered zero offset.
- Zero Range
- The entered zero range at the zero conditions
- Zero Temperature
- The entered zero conditions temperature. This value was used to calculate the muzzle velocity and mach number at zero conditions.

The output table contains drop and windage (or drop and windage deltas) for each range, temperature and altitude combination. To find the bullet drop, find the altitude closest to the actual shooting conditions. Under that altitude, find the temperature closest to the shooting conditions. Under that temperature, go down to the range for which the drop and windage are desired. The bullet drop (or delta) is in the top of the row, the windage on the bottom.