# Summary

Bullets fired from handguns follow general rules of physics and behave like gyroscopes. The angular motion of these bullets can be understood as a superposition of two oscillations, most easily be demonstrated by a two arms model.

Practically all handgun bullets are statically stable, many pistol and revolver bullets even have excessive static stability.

However, dynamic stability is not automatically guaranteed. Some bullets are dynamically unstable at the moment they leave the muzzle, others may loose dynamic stability during flight after being decelerated.

At the moment no reliable method exists, except experimentation, to foresee dynamic bullet instability, especially at long ranges. Some highly sophisticated computerized procedures (numerical solutions to the Navier-Stokes equations) to attack these problems are just being developed by ballistic researchers.

# Acknowledgements

I want to thank Prof. Dr. J.G. Hauck, Dresden for reviewing the manuscript and his most valuable suggestions to improve this document.

The experimental determination and evaluations of the yawing motion of various spin-stabilized handgun bullets were carried out at the German army proving ground WTD91 in Meppen. I have to thank this organization for leaving me the reports containing those unique and extremely valuable results.

The long-range Doppler tracking radar measurements of the 7.62 x 51 Nato bullet were made available to me by WEIBEL equipment, Gentofte, Denmark.

I want to thank Mr. Gaylan Warren, Columbia International Forensics Laboratory and AFTE webmaster, who made it possible that this document could be published in the world-wide-web.

# References

[1] Nennstiel, R., AFTE Training Seminar, 5.6.-9.6.1995, San Diego, CA USA

[2] Nennstiel, R., "How do bullets fly?", AFTE Journal, Vol.28, No.2, April 1996, S.104-143

[3] Nennstiel, R., "EBV4 User's Manual", Exterior Ballistics for the PC, Wiesbaden, Germany, 1995.

[4] Farrar, C.L., Leeming, D.W., Military Ballistics - A Basic Manual, Brassey´s Publisher Limited, Headington Hill Hall, Oxford OX3 0BW, England, 1983.

[5] Giles M.J., Leeming D.W., "An Aerodynamic Model for Unstable Projectiles", Proc. of the 11th Int. Symp. on Ballistics, Brussels, May 9 - May 11, 1989.

[6] Piddington, M.J., "Aerodynamic Characteristics of the 7.62 mm Nato Ammunition", BRL MR 1833, Aberdeen Proving Ground, Maryland, USA, 1967.