Ballistics engineers need to know how to calculate the ballistic coefficient from a bullet shape. The ideal way to do this is to test the bullet shape in a lab to determine its drag coefficient. However, tables often are used to look up the drag coefficients of common bullet shapes, described by letter and number designations. G1, the most common shape used as a reference, has a drag coefficient of ~0.5191. The formula for calculating the ballistics coefficient for bullets is BC = M/((CB/CG)*d^2), where BC is the ballistics coefficient, M is the mass of the object, CB is the drag coefficient for that particular bullet, CG is the drag coefficient of the G1 model, and d is the diameter of the bullet.
Instructions
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1
Identify the drag coefficient of the bullet shape by testing or referring to a table. For example: For the G1, the drag coefficient 0.5191 is commonly used.
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2
Measure the diameter and mass of the bullet if you do not already have this information. The diameter is the same as the caliber of the bullet if you measure in inches. Use either kilograms and meters or pounds and inches. For example:
The bullet has mass 0.0162 kg
The bullet has diameter 0.01143 m
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3
Plug all information into the equation and calculate the ballistics coefficient.
For example:
BC = M/((CB/CG)*d^2)
BC = 0.0162/((0.5191/0.5191)*0.01143^2)
BC = 0.0162/(1*0.01143^2)
BC = 124.