ballistics

ballistics, science of projectiles. Interior ballistics deals with the propulsion and the motion of a projectile within a gun or firing device. Its problems include the ignition and burning of the propellant powder, the pressure produced by the expanding gases, the movement of the projectile through the bore, and the designing of the barrel to resist resulting stresses and strains. Exterior ballistics is concerned with the motion of a projectile while in flight and includes the study not only of the flight path of bullets but also of bombs, rockets, and missiles. All projectiles traveling through the air are affected by wind, air resistance, and the force of gravity. These forces induce a curved path known as a trajectory. The trajectory varies with the weight and shape of the projectile, with its initial velocity, and with the angle at which it is fired. The general shape of a trajectory is that of a parabola. The total distance traveled by a projectile is known as its range. A ballistic missile in the first stage of its flight is powered and guided by rocket engines. After the engines burn out, the warhead travels in a fixed arc as does an artillery shell. In criminology the term ballistics is applied to the identification of the weapon from which a bullet was fired. Microscopic imperfections in a gun barrel make characteristic scratches and grooves on bullets fired through it, but use causes the marks a particular gun makes to change over time.

Science of propulsion, flight, and impact of projectiles. Internal ballistics deals with propulsion of projectiles, such as within the barrel of a gun or at a rocket launch. Guns and rocket engines convert chemical energy of propellants into kinetic energy of projectiles. External ballistics deals with projectile flight. The trajectory, or path, of a projectile is subject to the forces of gravity (see gravitation), drag, and lift. Terminal ballistics deals with the impact of projectiles on a target. Wound ballistics deals with the mechanisms and medical implications of trauma caused by bullets and explosively driven fragments, such as shrapnel.

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Ballistics (gr. βάλλειν ('ba'llein'), "throw") is the science of mechanics that deals with the motion, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.

A ballistic body is a body which is free to move, behave, and be modified in appearance, contour, or texture by ambient conditions, substances, or forces, as by the pressure of gases in a gun, by rifling in a barrel, by gravity, by temperature, or by air particles. A ballistic missile is a missile only guided during the relatively brief initial powered phase of flight and its course is subsequently governed by the laws of classical mechanics.

In the field of forensic science, forensic ballistics is the science of analyzing firearm usage in crimes.

Gun ballistics

Gun ballistics is the study of projectiles from the time of shooting to the time of impact with the target. Gun ballistics is often broken down into the following Three categories, which contain detailed information on each category:

• Internal ballistics, the study of the processes originally accelerating the projectile, for example the passage of a bullet through the barrel of a rifle;
• Transitional ballistics, (sometimes called intermediate ballistics)- the study of the passage of the projectile through space or the air; and the study of the projectile's behavior when it leaves the barrel.
• External Ballistics, the study of the interaction of a projectile with its target, whether that be flesh (for a hunting bullet), steel (for an anti-tank round), or even furnace slag (for an industrial slag disruptor).

Forensic ballistics

Forensic ballistics involves analysis of bullets and bullet impacts to determine the type. Separately from ballistics information, firearm and tool mark examinations involve analyzing firearm, ammunition, and tool mark evidence in order to establish whether a certain firearm or tool was used in the commission of a crime.

Rifling, which first made an appearance in the 15th century, is the process of making grooves in gun barrels that imparts a spin to the projectile for increased accuracy and range. Bullets fired from rifled weapons acquire a distinct signature of grooves, scratches, and indentations which are somewhat unique to the weapon used.

The first firearms evidence identification can be traced back to England in 1835 when the unique markings on a bullet taken from a victim were matched with a bullet mold belonging to the suspect. When confronted with the damning evidence, the suspect confessed to the crime.

The first court case involving firearms evidence took place in 1902 when a specific gun was proven to be the murder weapon. The expert in the case, Oliver Wendell Holmes, had read about firearm identification, and had a gunsmith test-fire the alleged murder weapon into a wad of cotton wool. A magnifying glass was used to match the bullet from the victim with the test bullet.

Calvin Goddard, physician and ex-army officer, acquired data from all known gun manufacturers in order to develop a comprehensive database. With his partner, Charles Waite, he catalogued the results of test-firings from every type of handgun made by 12 manufacturers. Waite also invented the comparison microscope. With this instrument, two bullets could be laid adjacent to one another for comparative examination.

In 1925 Goddard wrote an article for the Army Ordnance titled "Forensic Ballistics" in which he described the use of the comparison microscope regarding firearms investigations. He is generally credited with the conception of the term "forensic ballistics," though he later admitted it to be an inadequate name for the science.

In 1929 the St. Valentine's Day Massacre led to the opening of the first independent scientific crime detection laboratory in the United States.

See also

• Ballistic fingerprinting
• Ballistic conduction (to do with electron transport)
• Bullet
• Cartridge
• Gun
• Gunshot residue
• Physics of firearms
• Trajectory
• Vaporific Effect
• Gunshot injury
• Stopping Power
• Association of Firearm and Tool Mark Examiners
• Mechanics

References

External links

• Ballistic Trajectories by Jeff Bryant, The Wolfram Demonstrations Project.

Ballistic comparison

• Ballistic Chart
• AmmoGuide
• Federal Cartridge
• JBM Small Arms Ballistics — Trajectory and related calculators