External Ballistics

While interior ballistics deals with events inside a gun, exterior ballistics covers those events that occur from the time the bullet leaves the muzzle until it strikes the ground downrange. The program will allow you to calculate and plot trajectories, determine downrange bullet information (energy, velocity, bullet drop, etc.), and calculate point blank range.

Trajectory

When a bullet leaves the gun, it contains kinetic energy and the bullet attempts to move in a straight line with its initial velocity. However, gravity pulls the bullet toward the earth and air resistance impedes the bullet's progress. The result of these forces cause the bullet to follow a drooping curve called a trajectory, and the bullet soon strikes the earth downrange. Based on muzzle velocity and ballistic coefficient, the bullet's position and remaining velocity and energy can be calculated at any point downrange.

Once the last input is entered for a particular Trace, the tabular results will be displayed in the upper right section of the screen. It will also show graph results. The program allows you to input data on three bullets. It will provide plots on all three traces on the same graph for a comparison of traces. You may also change the graph type. The available graphs are:

• Bullet Height vs. Range
• Bullet Velocity vs. Range
• Bullet Energy vs. Range
• Taylor Index vs. Range
• Wind Drift vs. Range
• Time of Flight vs. Range

You may enlarge either the table of values or the graph to full size. You can also save the graph as a bitmap file (*.bmp) for use in other programs (e.g. inserting a bitmap image into a word processing document such as MS Word).

You can also see the information for making zero adjustments. The trajectory table shows the zero adjustment in minutes of angle (MOA). And you can click the "Click Chart" button for the chart of scope adjustments in clicks.

Downrange Bullet Energy and Velocity

This section of the program will calculate ballistics data at your specified downrange distance. This data includes muzzle energy, terminal velocity, terminal energy, flight time, bullet drop, taylor index, and wind drift.

Point Blank Range

Point Blank Range is the maximum distance above and below the line of sight the bullet will pass for a given range. For this program you may choose any value between 2.5 and 5 inches. Typically a maximum trajectory height of 2.5 inches (or 5 inches maximum spread) is used for small caliber bullets fired at high velocity while a trajectory height of 5 inches (or 10 inches maximum spread) is used for big game cartridges.

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