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Calculating Ballistic Coefficients from Known Velocities and Ranges
The ballistic coefficient of a bullet, as it applies to a certain Drag Table, may be determined by comparing distance required for the test bullet to lose a certain amount of velocity and then compare that distance to the distance required by the model bullet associated with the Drag Table to lose the same amount of velocity.
Some bullet manufacturers such as Lyman and Sierra have performed tests that indicate multiple ballistic coefficients through various velocity ranges are necessary to accurately compare most bullets to a certain drag table.
This software is designed to calculate the ballistic coefficients throughout at least five consecutive velocity ranges and then to perform ballistics and trajectory calculations utilizing these multiple coefficients and their associated ranges.
To calculate a series of one to five ballistic coefficients, first select the Calculate B.C.s radio button and then select the number of ranges to be used in the calculations. This will open the consecutive entry fields where the beginning velocity of the range, the distance of the range and the final velocity of that range may be entered. Once the velocity and range data is entered, the Drag Table is selected, the weight of the bullet is entered and then the "Calculate the Ballistic Coefficient" button is clicked. The ballistic coefficients are then calculated for each associated velocity loss and range distance.
If desired, a test trajectory may be computed, applying the indicated ballistic coefficients as the bullet passes through the respective velocity ranges. Clicking on the Calculate a Test Trajectory will move the focus to the Data Entry page where the starting velocity and successive ranges listed for the ballistic coefficient calculation may be entered. These entries may then be used to compute the ballistics and trajectory calculations. Other velocity and range values may be entered so long as the Muzzle velocity value is not greater than the starting velocity used to calculate the ballistic coefficients.
If the calculated coefficients are acceptable, return to the "B.C. From Velocities" page and enter the remaining vital bullet data by clicking the "Enter Bullet Details" button. After the information is correctly entered, clicking the "Save Bullet" button will store a record of the bullet and it's associated velocity ranges and their associated ballistic coefficients in the Active Bullet database, where the record may either be used for further calculations or moved to either the Jacketed or Cast bullet database.
If multiple ballistic coefficients of a bullet are known, or are being successively estimated, throughout a trajectory, the velocity ranges and their associated coefficients may be entered here by selecting the Enter BCs radio button, selecting the number of coefficients to be entered and then following the same procedures outlined above to test and store the bullet information.
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