Using Exbal on the Pocket PC
Exbal Version 4.1


Exbal for Palm hand held devices uses the same rigorous ballistic motion basis that is used on the PC version.  There are six forms (three primary and three optional) on the hand held version for inputting data and performing the calculations. The output form displays the ballistic data at a user specified target distance.

The hand held version of Exbal also has a “Data Manager” which enables the user to develop and maintain multiple sets of data.

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Bullet Data, Field Conditions, Target Data, And Results
Each of the three primary forms has fields to enter data and push buttons to move onto the next logical form or to return to the main form and menu.  The first logical form is the “Bullet Data" form, which has fields to specify bullet weight, sight in distance, distance between line of sight and line of bore, and the ballistic coefficient of the bullet.  A check box is used to specify that the sight in distance should be meters rather than yards.  Push buttons are used to go to the next logical form or to the main form.

The second logical form is the “Field Conditions” form, which has input fields to specify muzzle velocity and current atmospheric conditions at the target location. These include altitude, temperature, pressure (not corrected to sea level), and relative humidity.  A check box is used to indicate that system should calculate pressure based on altitude.

The third logical form is the Target Data form, which has input fields to specify target distance, wind speed, wind direction, target speed, and incline angle to target. A check box is used to specify that the target distance should be meters rather than yards. A push button is used to start the ballistic calculations.  Another push button is used to return to the main form and menu.

                                 Bullet Data                                                                 Field Data


                                Target Data                                                            Ballistic Coefficients


Optional Input Forms

Sight In Data, Ballistic Coefficients, Sight Adjustment Options

Three optional forms are provided to enable additional specifications.  The "Sight In Data" form is used to specify the conditions at the time that the rifle was sighted in which may be significantly different than the conditions at the target location.  There are input fields for muzzle velocity, and atmospheric conditions at the time of sight in.  A check box (automatically set by default) is used to indicate that the sight-in conditions are the same as those specified under “Field Conditions” above.

The multiple "Ballistic Coefficients” form is used to specify bullets that have ballistic coefficients that change with velocity. Examples of these are the high efficiency Sierra MatchKing target bullets.  The 30 caliber 168 grain MatchKing is illustrated in the following display.

The interpretation of this data is as follows:  For velocities exceeding 2600 fps the ballistic coefficient is 0.462, for velocities between 2600 and 2100 fps the ballistic coefficient is 0.447, for velocities between 2100 and 1600 fps the ballistic coefficient is 0.424, and for velocities less than 1600 fps the ballistic coefficient is 0.405.  There is an excellent discussion in the Sierra Reloading Manual of how the need for multiple ballistic coefficients was discovered.

The fact that the ballistic coefficient changes as velocity changes is taken into account when Exbal performs the ballistic motion equations.

The "Sight Adjustment Options" form is used to specify the units of sight correction for elevation, windage, and target lead (for moving targets). In the display of results, both inches and “clicks” are displayed. The default units of sight adjustment (clicks) are one minute of angle (approximately one inch per hundred yards).  Many target scopes have dial readings for windage and elevation in minutes of angle. Other scopes have click stops for 1/8, ¼, ½, or one minute of angle. Still other scopes have internal gradient lines or dots to indicate minutes of angle and/or mil-radians (mil dot).


                Sight Adjustment Specifications                                            Sight-in Conditions


The Pocket PC version has two data look up functions. The first one provides look up of ballistic coefficients provided by the bullet manufacturers.  The second one provides look up of velocity data for factory loaded ammunition.

                     Look up Ballistic Coefficients                                    Look up Velocity Data


Exbal provides two output windows. The "calculate" button shows the ballistic data for the specified target. It contains all of the information about the bullet at the target point.  The "drop table" button provides the sight adjustment data needed at a series of target distances.

                                Calculation Results                                                     Drop Table


   Exbal Utility Functions

Three "utilitiy" functions are provided to enable the shooter in the field to make adjustments. First there is the Match Sight-in Point function which calculates the true zero point based on the bullet impact at a specified distance. Second there is the Trajectory Correction Function which uses a known sight-in distance (zero point) and calculates the velocity that matches impact point at a known distance.  And finally there is the Range Estimation Calculator which does the math associated with using a ranging reticle to estimate target distance.

                            Match Sight-in Point                                                  Trajectory Correction


                            Range Estimator                                              


Ballistic Reticle Analysis For The Pocket PC Version of Exbal:  

Scopes with ballistic reticles are increasingly being used by long range shooters and they have been used by military "snipers" for many years.  They offer an alternative to making external scope adjustments to compensate for bullet drop at longer ranges.

The concept of the ballistic reticle is introduced on web page.  A ballistic reticle consists of a main cross-hair and a series of aiming reference points (bars, circles, or dots) which are spaced along the vertical cross-hair.  Information about specific reticles can be obtained from Swarovski/Kahles, Burris, Leupold, Nightforce, and other vendors who offer them with their scopes.

To illustrate this concept, the set up window and point blank range analysis results are shown for a 308 Win, 175gr MatchKing bullet at 2600 fps, sighted in at 100 yards, shooting at a target 600 yards away.  The reticle being illustrated is a Nightforce NP-R2 reticle, which has 10 reference bars spaced at 2 MOA intervals.

The Point Blank Range results for this particular case indicate that Bar #8 should be used.  (the zero point for Bar #8 is 592 yards so the bullet will strike about 2 inches low)  The beauty of this approach is that no external scope adjustments were needed. 

                         Ballistic Reticle Analysis                                        Point Blank Range Analysis


Now the Palm version of Exbal will calculate how the use of a ballistic reticle will affect the bullet impact point compared to the aiming reference point used.   There are new windows to support this analysis. The first window enables the user to select retcle data from a list of reticles. The second window is used to manually specify the configuration of the ballistic reticle being used.  This is where the measurement system (MOA, IPHY, or MILS) and the angular difference between the main cross-hair and each of the aiming reference points (bars, circles, or dots).  For simplicity the reference points are labeled Bar #1, Bar #2, etc.

There are three different measurement systems used to specify the angular difference between the horizontal cross-hair and the aiming reference points (bars, circles, dots).  First there is the traditional "minute of angle" or MOA which is equivalent to 1.048 inches per 100 yards.  The second system is "inches per 100 yards" or IPHY.  And the third system is "mil-radians" or MILS (1 meter per 1000 meters) which is equivalent to 1 yard per 1000 yards or 3.6 inches per 100 yards.


                     Ballistic Reticle Selection List                                        Edit Reticle Specifications


Two optimization functions have been added.  The first function determines what sight-in distance should be used so that a particular bar will strike the target center at the specified target distance. The second function  determines what operating power the scope must be set at to achieve making the zero point of the specified bar equal to the target distance. The second function  is only applicable to scopes that have the reticle in the second focal plane. If the spacing of the bars or dots remains constant while the image size changes with power, the reticle is in the second plane.

              Calculate Optimum Sight-in Distance                              Calculate Optimum Power Setting