If you have a scope with subtension markings on the reticle, this utility will compute the trajectory ranges which correspond to the BDC (Bullet Drop Compensation) markings for a particular cartridge.
To compute the target distances you will need to have the MOA or MIL data which correspond to the markings. Some manufacturer's provide this information on-line or you can send a message to customer support requesting them.
Some scope manufacturers provide a data sheet which list distances for a number of popular caliber and bullet weights. These must be used judiciously since the specifics of the cartridge (ballistic coefficient, muzzle velocity) and rifle (sight height) may not be provided or not match the cartridge you are interested in.
Nikon's Spot On app will also compute subtension ranges for a specific cartridge, if you have a Nikon scope. It is very good.
Note that the MOA/MIL data is magnification specific. You may only be provided with the MOA/MIL values for the minimum and maximum magnification settings. If you wish the values at an intermediate magnification setting, they can be determined by taking the smallest magnification value and dividing it by the multiplier needed to get the value at the desired magnification. An example is below:
You have a 3x12 scope with a MOA value of 8.00 for the 3x BDC1 setting. The MOA value for the 6x BDC1 setting is (8.00 / 2) = 4.00 MOA since 6x / 3x is 2. The MOA value for the 9x BDC1 setting is (8.00 / 3) = 2.667 MOA since 9x / 3x is 3. To verify, check that the computed value for the 12x BDC1 setting (8.00 / 4) matches the value provided by the scope maker.
The most useful values will normally be those for the highest scope magnification, since you will usually use the highest scope setting for long range shots.
The 1-Shot Show Scope BDC Distances utility is accessed from the Single Gun and Cartridge screen. If you wish to have environmental corrections performed on the bullet trajectory, apply them before selecting the Show Scope BDC Distances button. Also ensure that the scope zero distance has been set as you require. This can be done by either:
Long clicking the gun in Select Gun and Cartridge, or
Selecting Change Scope Zero Distance in Shooting Utilities.
On the Scope BDC Distances view:
Set the distance units as you require in Select Input Units (Yards, Feet, or Meters).
Set the Scope BDC Units (MOA or MIL)
Type in the Scope Description and Scope Magnification information if you wish to save the computation results.
Enter the Scope BDCn data provided by the scope manufacturer.
Select the Compute button to determine the trajectory ranges which correspond to the BDCn subtension markings. Note that the maximum range supported is 1000 meters. The distance for any range which exceeds 1000 meters will be left blank.
Select the Save button to write the computed data to a csv file in the 1-Shot folder of the Downloads directory. The file name is taken from the Scope Description. The data in the file is separated by commas (“,”).
Select the Done button to exit the view.