Ballistics is also used to describe the process of
identifying a
firearm through test firings and careful examination of spent
casings and
bullets from those firings. It is a process used daily by
law enforcement personnel all over the world, as well as by those designing and testing new (or restored) firearms.
More in line with Webster1913's definition, it (in another incarnation) is the study of the flight and energy transfer of projectiles, usually from firearms, for purposes other than identification. For example, hunting (in many nations/states/provinces) is regulated as to the type of ammunition that is permitted for use against various targets. The reasoning is fairly straightforward; you wish to ensure that the hunter is safely employing a weapon; one that (when properly wielded) will kill the target quickly and cleanly, without causing it painful and debilitating (but not fatal) injury.
There are reasons other than strict humanitarianism for this. For one, it helps to ensure that a minimum number of animals are destroyed per hunter. For another, it helps to ensure the safety of people and property; for example, while hunting for fowl with a shotgun and shot shells is quite sensible, hunting for those same creatures with a rifle is foolhardy. Not only are your chances of success much reduced, but a rifled bullet (especially when aimed in an upward direction as it would be when hunting birds) will carry an enormous distance - miles, in many cases. When it strikes the ground it will not be going as quickly as it did leaving the gun, due to friction, but it will be going fast enough to cause fairly severe damage to anyone or anything that it hits. Round shot packed into a shell, with lower pressure and more chaotic flight patterns, will fall harmlessly to the ground in as little as a hundred feet. (WARNING: Don't stand in front of them to check.)
In any case, the desire to ensure a clean kill overlaps to some degree (actually, sometimes is a complete Boolean OR) with military ammunition design. Due to various treaties and agreements, there are limitations on the types of bullet that can be used in an antipersonnel weapon such as the rifle, carbine or pistol. These are not always designed to reduce the 'cleanliness' of the shot, or increase damage, as might be assumed. The ideal disposition of an enemy soldier is not, in fact, dead. Rather, the ideal outcome (from a military standpoint) is to succeed in incapacitating as many enemy soldiers through injury as possible, without killing them. The reasoning is fairly simple; a dead soldier consumes no resources, whereas a wounded one (assuming policy calls for it) will occupy the time and supplies required to transport, protect and heal him or her back to fighting condition.
So, in the guise of humanity, one example of a convention on ammunition is the specification for all military wartime ammo to have a full metal jacket. This not only allows it to travel through light obstructions without slowing appreciably, but ensures that when it hits it is more likely to bore a hole than to fragment and transfer all of its energy to the target. This is directly opposite the ideal self-defense or law enforcement pistol ammo, which ideally transfers all its energy to the target without passing through and harming anything or anyone behind said target. In addition to protecting bystanders, this means that the target in question is more likely prevented from doing harm to the shooter or anyone else.
Anyhow, as one might imagine, the amount of energy a bullet carries (measured in joules) can be quite important to hunters, policemen, military planners ,and private firearm owners, if for differing reasons. That energy is determined by two factors - the mass of the bullet and the muzzle velocity with which it leaves the gun. With that in mind, here are some rough energy levels for some of the more popular bullet types and calibers.
Cartridge Caliber/mm Bullet mass (g) Muzzle Velocity Muzzle Energy (joules)
-----------------------------------------------------------------------------------------------------
.45 ACP .45 16.8 g 259 m/sec 850 fps 540 joules
9mm Parabellum 9mm 7.5 g 366 m/sec 1,200 fps 475 joules
Centerfire Hornet .22 3.0 g 820 m/sec 2,690 fps 1,009 joules
Remington NATO .223/5.56mm 3.6 g 1,006 m/sec 3,301 fps 1,822 joules
M1 Carbine .30 7.1 g 607 m/sec 1,991 fps 1,308 joules
Winchester .30-30 9.7 g 728 m/sec 2,388 fps 2,560 joules
Soviet AK-47 7.62mm 8.0 g 715 m/sec 2,346 fps 2,045 joules
Lee-Enfield .303 11.7 g 770 m/sec 2,526 fps 3,469 joules
Winchester,NATO,FN .308/7.62x51mm 11.7 g 3,744 joules
Winchester .458 Magnum 33.0 g 643 m/sec 2,110 fps 6,822 joules (1)
Dakota .450 Magnum 32.4 g 747 m/sec 2,451 fps 9,040 joules (2)
Weatherby .460 Magnum 32.4 g 793 m/sec 2,602 fps 10,187 joules (3)
Browning MG .50 caliber 46.7 g 857 m/sec 2,812 fps 17,149 joules (4)
(1) Used for big game hunting, known as the 'Africa' round
(2) This is a custom cartridge for the Dakota 76 Rifle, a hunting piece
(3) Weatherby makes hunting rifles only, in various Magnum calibers from .224 to .460
(4) Used in the Browning 50-cal machine gun (as well as recent sniper rifles like the Barrett 50-cal).
First developed in 1921 by John Moses Browning.
As you can see, there is a wide variety of power available in ammunition. Note that the higher the energy delivered to the bullet, the more punishing the recoil on the shooter, as well (ameliorated somewhat by the mass of the gun).
Final note: the study of the energy transfer from the gun/cartridge to the bullet, and the resulting trajectory, is sometimes called initial ballistics. This is as opposed to terminal ballistics, which is concerned with the interaction between the bullet at the target (or whatever it hits) and the consequences for both. This includes shock damage, penetration, deformation of the bullet, etc. For an example of how this can be applied, see this manufacturer's propaganda:
http://www.hawkbullets.com/terminal.htm
Sources and recommended reading:
- Ballistics calculator at: http://www.zvis.com/bvjtools.shtml
- Hartink, A.E. Encyclopedia of Rifles and Carbines. Rebo Productions, 1997: Lisse, The Netherlands.
- Remington Rimfire Ballistics at: http://members.dandy.net/~billc/10_22stuff/remdata.htm
- Rinker, Robert A. Understanding Firearm Ballistics. Mulberry House, 1999: Apache Junction, Arizona (not kidding).
- Pejsa, Arthur. Modern Practical Ballistics. Kenwood Publishing, 1991: Minneapolis, Minnesota.