ABSTRACT
As the bullet emerges from the muzzle of the gun, it is suddenly released from the rigid constraining action of the barrel walls, and as a consequence is immediately acted on by the bu¦eting forces of air resistance, which will attempt to destabilize it further. “e bullet will only have its long axis perfectly in line with the bore by chance at this point due to the disturbing e¦ects caused by its sudden release. Any condition of yaw will allow the cyclone-like wind opposing the bullet to act against its sides, thus acting to slow it down and increase its angle of yaw further. “ese forces will act on a point in the bullet referred to originally by Leonardo da Vinci as “the center of pressure,” which in most bullets will lie somewhere between the bullet tip and its center of gravity. “is is when the powerful gyroscopic spin imparted on the bullet by the ri—ing in the barrel acts to restabilize the missile by forcing its point back into its original intended alignment just before leaving the muzzle. “roughout its —ight through the atmosphere the bullet will continue to su¦er the bu¦eting e¦ects of air resistance, and periodic lesser irregularities will occur during its —ight (Figure 6.1). However, assuming that the bullet’s construction is sound and that the correct rate of rotational spin
has been imparted on it, then its —ight will follow a normal trajectory within conventional conditions of use. Insu›cient spin on the bullet will lead to unstable —ight, eventually resulting in the bullet tumbling end over end with the loss of all hope of accuracy. I have dealt with instances in which crude improvised smooth-bore barrels have been £tted to £rearms subsequently used with bulleted ammunition. “e e¦ects are apparent during the examination of damage at the scene of the incident or on the body in the form of abnormal elongated bullet entry holes, and in some instances the bullet hole has clearly resembled the pro£le of the bullet. Other factors also in—uence the otherwise stable —ight of the bullet. “ese include the precision with which the bullet has been manufactured, such as its symmetry, di¦erences in the thickness of its jacket, voids and slag within its core, and the condition of its base on which high-pressure gases exert their accelerating force. Serious target shooters and hunters select only precision-made bullets when loading their ammunition, or use cartridges manufactured to known high standards.
“e other major forces that exert their in—uence on the bullet include the force of gravity, which acts to pull the bullet downward toward the earth at a rate of acceleration of approximately 32.2 ¡/s2 (9.81 m/s2); the resistance of
the opposing wind forces previously mentioned, which slow the bullet down, thus stripping from it both velocity and retained kinetic energy, and crosswinds will act to push the bullet sideways from its intended course.
