When you first start the program, a title displays the necessary credits while the initial information for the screens and computations loads. The time-consuming operation during this period is the loading
of the information computed during the last session. (On Initial start-up, we provide a pre-computed data set using the Sierra Bullets we love the most.) This data set contains the complete trajectory information, including the bullet trajectory and environmental parameters with which each trajectory was computed, for the five active bullets last used in the program. Thus, the user can resume operations where the last session ended.
Once these data have been loaded, the initial screen appears with the menu and toolbars. The program initializes in the Trajectory operation showing the Trajectory Parameters panel on the right side of the monitor and with the Current Bullet from the last session highlighted in the Active Bullets window. The Menu bar operates just as the normal MS Windows or MS Office menu bar in that left clicking on a menu item drops down the sub-menu items that can be performed. An example of this can be found by left clicking on the Operations menu item to drop down the available operations (Trajectory Calculation, Point Blank Range Calculation with a Given Zero, Maximum Point Blank Range Calculation, Elevated Fire, Calculate Zero, Maximum Range Calculation, Vertical Fire and Trajectory Comparison). Right-clicking the mouse with the cursor located anywhere on the left panel of the screen and outside a defined window will bring up the same Operations in a panel on the screen. A similar function (Right-Click) has been included in the right panels to switch between the Trajectory Parameters panel and the Environment Parameters panel. The user may select any of these operations to perform.
If the user has selected a new bullet or has not run a baseline trajectory on a new bullet and one is required for the commanded operation, the baseline trajectory will be run automatically prior to
performing the commanded operation. The baseline trajectory will be run using the values specified in the Trajectory Parameters and Environment Parameters panels located on the right portion of the screen. Thus, the user should review these panels when a new bullet is loaded to assure they are consistent with the bullet.
While selecting and loading a new bullet from the Load Bullet menu item should be self-explanatory, it should be noted that loading a new bullet replaces the currently selected (highlighted) bullet. With the exception of the parameters unique to the specific bullet (and a typical muzzle velocity) the new bullet will receive the same trajectory and environmental parameters that were present for the bullet being replaced. For example, if the bullet being replaced was run with a 1000 yard maximum range, the bullet replacing it will also have a 1000 yard maximum range. This may be undesirable for a bullet like the .458 diameter 300 gr. Flat Nose for the .45-70.
Placing the cursor on any individual button on the toolbar just below the menu bar will bring up a label that defines the button’s functions. Reading from the left, the first button will permit editing a custom bullet. The second will print. The third is reserved for a Print Preview function. The fourth button will return to the chart (table) mode when available, and the fifth button will switch from the chart mode to graphics output when available. The sixth button will hide/show the data entry panels for those users with 640 x 480 screens to permit viewing of the entire output box. Note that a trajectory must be calculated prior to utilizing the graphics output mode. The next command buttons are only effective in the graphics mode to add/remove the trace label box, add/remove grids, add/remove labels on the graph, and zoom the graph.
The Trajectory operation is designed to calculate the baseline trajectory of a selected bullet. It handles an elevated fire case where the shooting range is not level. It will handle up to +/- 65 degrees. The results are stored into the current bullet locations as the baseline trajectory for that bullet. You may change the information as defined on either the Trajectory Parameters panel or the Environment Parameters panel as you desire. However if you change anything, you must left-click the Accept Data control to make the change effective. You must then left-click the Calculate control to calculate the trajectory.
There are two operations associated with Maximum Point Blank Range. The first calculates the Maximum Point Blank Range of your weapon as you have zeroed it. That is, given that you choose a vital zone for your target or game animal and you have zeroed your gun in for a specific range, this operation will calculate whether your zero is such that the bullet will rise farther than one-half the vital zone height above your line of sight prior to reaching your specified zero range (point blank zero less than your zero range), and when it will be more than one-half the vital zone height below your line of sight at ranges farther than your zero. It will also determine if your zero range is less than the zero range for maximum point blank range. In either case, the maximum point blank range is determined for your gun as sighted.
The second operation associated with Maximum Point Blank Range determines what the optimum zero range is to maximize the point blank range of your particular bullet given any reasonable vital zone height. We arbitrarily determined a limit of 36 inches for the vital zone height assuming that some hunters might be going after the few elephants left! The operation is performed on your selected bullet and its baseline trajectory.
The Uphill-Downhill operation calculates the difference between your reference trajectory (which may have been computed for a non-level range) and the elevated (or depressed) firing angle. The printout will define the bullet path difference directly as a separate column in the tabular output. The remaining values in the table (remaining velocity, energy etc.) are based on the new trajectory at the new
elevation angle so that the remaining differences at the elevation angle can be calculated from the reference trajectory output data. The reference trajectory is not destroyed so repetitive trajectories can be run without changing the reference trajectory.
The Calculate Zero operation is designed to answer the question ―I’m sighted in ―x‖ inches high at ―Y‖ yards. What’s my zero range? The program permits measured bullet path height input to .01 inches (for those purists who believe that they can reliably determine the centroid of their group to .01 inches) and range increments of 1 yard out to 1000 yards. Only positive (above the line of sight) values are accommodated.
The Maximum Range operation computes the maximum range of your selected bullet given the environmental conditions of your site (altitude, temperature, pressure and humidity), a reference slope angle, and the muzzle velocity of your bullet. The reference slope angle is designed to support determining whether the bullet will clear an object or not. The Maximum Range is determined with respect to this slope. A zero-degree value is level fire. The program outputs the maximum range along the reference slope and the bore elevation angle with respect to level (horizontal direction) necessary to achieve it.
The Vertical Fire operation determines the maximum altitude that the selected bullet will reach given the muzzle velocity, firing point altitude, and environmental conditions defined by the user. This is a special algorithm for vertical fire. Since winds may vary in direction and magnitude at different altitudes (and almost always do!), there is no provision for wind. The program outputs maximum altitude in feet (or meters) above sea level, maximum height above the firing point, time of flight to the maximum point, and the environmental conditions at the firing point.
The Trajectory Comparisons operation permits graphic comparison of up to five bullets. The values that can be compared graphically are remaining velocity, remaining energy, drop, bullet path and wind drift. Only trajectories with like computational units (English or Metric) can be compared. Since the graphs are plotted in 1-yard (or meter) increments, printout range increments, maximum ranges and zeros need not be the same. The zoom function clearly makes the value labels on each plot more readable, although for closely matched bullets it still requires some interpretation.
The Trajectory Variations menu item permits a ―what if‖ function. It is much the same as the Uphill- Downhill operation in that the reference trajectory is preserved for all calculations. The output table gives a specific bullet path difference column for the difference between the reference trajectory and the trajectory computed with the variations input data. The values in the body of the table are for the trajectory with the variations included. Note that there are four panels of information that can be varied to observe the effects on the bullet trajectory. Graphic output is available showing the
velocities for both the reference and the variations trajectory. Those of us who hunt at altitudes and in weather conditions other than those at which we sight-in, use this operation to get an accurate feel for where the rifle shoots under real conditions.