# Introduction

This document is an improvement of a presentation given by the author at the 1995 AFTE meeting in San Diego, CA (see reference [1]) and a publication in the AFTE Journal (see reference [2]). It is intended for the following readership:

- Hunters and sportsmen, having an interest in exterior ballistics,
- Students and teachers in exterior ballistics,
- Forensic firearm examiners, especially "newcomers" in the field.

The title of this document "How do bullets fly?" seems to be an odd question, and appears to be almost foolish when tried to be answered before this readership.

However, as in many fields of science and technology, studying a matter thoroughly, which at first sight seems to be simple, may bring into light complex and complicated facts and this is also the case with regard to the motion of spin-stabilized bullets fired from handguns.

Most people expect that bullets fly nose-forward and stable from the muzzle to the target. For short ranges, most trajectories could be approximated by a straight line, whereas the bending of the trajectory must be considered for longer ranges only.

Most firearm experts accept that bullets may tumble when grazing an object or when leaving an intermediate target. However, it will be outlined that some physical conditions must be fulfilled to guarantee stable flight, and handgun bullets are by no means automatically stable.

From a teacher's point of view, the motion of a spinning gyroscope is one of the most complicated motions which a student of physics has to be confronted with during the lectures of classical mechanics. Although the general motion of gyroscopes can be explained and completely understood only by a thorough mathematical treatment, this introduction makes an attempt to plausibilize the subject by means of numerous illustrations and the use of formulas is restricted to those who wish to see them (note various links to view formulas).

For the explanation of some general physical terms used in this article, the interested reader is requested to refer to an elementary physics textbook.

## How to use this document

I suggest to read this document according to the succession of chapters given in the main page. The main page can always be reached by a click on the button.

The button always returns you to the top of the currently selected page.

Within the text, you will find numerous links to figures and formulas. Viewing figures is highly recommended. Formulas can be viewed by those readers who are interested in a more mathematical description, however no mathematical derivations should be expected. A click on a button will return you to the text from a page displaying a figure or a formula.

This document is allowed to be copied and used freely for non-commercial use, especially for educational purposes. It is highly recommended to download this document and read it offline.