From the earliest cavemen to modern man, advantages have been sought in finding bigger, better weapons. In searching for better weapons stones were thrown, slings were developed, guns were produced, and missiles were invented. All of these developments involve a projectile flying through the air, and in order to better understand the nature of these projectiles the science of ballistics was developed.
Ballistics is the science that deals with the motion, behavior, and effects of projectiles, especially bullets, aerial bombs, rockets, or the like; the science or art of designing and hurling projectiles so as to achieve a desired performance. .
In the beginning of the study of ballistics as a science very little was known about the way an object flew. Originally it was believed that a "bullet- flew in a straight line directly from muzzle to target without any decrease in velocity. It was also believed that if the target was to far away that the bullet would fly until it came to a stop and then simply fall to the ground. Later, when guns with more firing power were introduced the gunner could actually see the ball fly in a curved path. .
This observation changed the way ballisticians viewed the effects on a projectile. They began to realize the effects gravity had on an object flying through the air. Though gravity was beginning to be understood, the effects of air resistance on the path of a bullet were not even considered, and the results were inaccuracies in gunnery that could not be explained. .
Most firearms operate by exploiting the same basic physical and chemical laws "it is therefore useful to study these principles independent of the form that the firearm takes. This is why the study of internal, external and terminal ballistics are so important.
Internal ballistics is what happens inside a weapon when it is fired. The firing pin makes a distinct mark on the cartridge. Then explosive pressure causes the bullet to expand slightly to fill the spiral 'rifling' grooves cut in the bore.