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External Ballistics


BTG Research has developed acoustic methods in external ballistics (measuring velocity and drag), measured the effect of intermediate barriers on projectile stability and accuracy, and measured ammunition performance for comparison with published specifications. In addition, field performance has been correlated with benchtop performance for various lead-based and lead-free primer compounds.  

External ballistics are dominated by a bullet’s muzzle velocity and ballistic coefficient, with rifle twist and bullet length also playing a role.  It is of interest to quantify bullet stability, bullet drop and wind drift, spin drift, and the velocity and kinetic energy retained by a bullet downrange. For example, the figure below at right illustrates the stability of a specific .30-06 rifle bullet as a function of the barrel twist rate and shows some of the effects of field conditions (temperature and altitude).

The sound of a bullet hitting a target is sometimes discernable in an audio recording of a shooting event and can be used to determine the distance from shooter to target.  For example, at left are sound spectrograms for three cases of a bullet hitting a deer. Impact times are shown with arrows for each case.  Color scale is logarithmic.  There is a considerable increase in acoustic energy in the 2-7 kHz range for 5-10 ms after impact in each case.  In case C, there is another increase in energy near 370 ms. 

Papers

A stability formula for plastic tipped bullets: Motivation and development of new formula.  (January 2012)

A stability formula for plastic tipped bullets: Experimental testing.  (February 2012)

Does polishing a rifle bore reduce bullet drag? (April 2011)

Using sound of target impact for acoustic reconstruction of shooting events.

The truth about ballistic coefficients.

Acoustic methods for measuring bullet velocity.

 

External Links

 

Ballistic coefficient defined

JBM Ballistics calculators

International Ballistics Society website