From Wikipedia, the free encyclopedia
Ballistics (gr. 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.
Firearm ballistics information can also be used in forensic science. 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.
Ballistics is sometimes subdivided into:
A ballistic missile is a missile designed to operate in accordance with the laws of ballistics.
The term ballistics is also sometimes used to refer to acceleration curves applied to the motion of a computer mouse.
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.
The Manufacture of Smokeless
Powders and their
Robert M. Heramb
Bruce R. McCord
Smokeless powders are a class of propellants that were developed in the late 19th century to replace black powder. The term smokeless refers to the minimal residue left in the gun barrel following the use of smokeless powder. In forensic analysis, smokeless powders are often encountered as organic gunshot residue or as the explosive charge in improvised explosive devices.
All smokeless powders can be placed into one of three different classes according to the chemical composition of their primary energetic ingredients. A single-base powder contains nitrocellulose, whereas a double-base powder contains nitrocellulose and nitroglycerine. The energetic ingredients in triple-base powders are nitrocellulose, nitroglycerine, and nitroguanidine, but because triple-base powders are primarily used in large caliber munitions, they are difficult to obtain on the open market.
Composition and Manufacturing
The major classes of compounds in smokeless propellants include energetics, stabilizers, plasticizers, flash suppressants, deterrents, opacifiers, and dyes (Bender 1998; Radford Army Ammunition Plant 1987).
Chemical composition is one important characteristic defining smokeless propellants; however, another important characteristic is its morphology. Shape and size have a profound effect on the burning rate and power generation of a powder (Meyer 1987). Common particle shapes of smokeless propellants include balls, discs, perforated discs, tubes, perforated tubes, and aggregates (Bureau of Alcohol, Tobacco and Firearms 1994; Selavka et al. 1989).
Morphology also lends clues to whether a powder is single- or double-base (Bender 1998). Most tube and cylindrical powders are single-base, with the exception of the Hercules Reloaderâseries. Disc powders, ball powders, and aggregates are double-base, with the exceptions being the PB and SR series powders manufactured by IMR Powder Company of Plattsburg, New York.
Except for ball powder, smokeless powder is manufactured by one of two general methods, differing in whether organic solvents are used in the process (Meyer 1987; Radford Army Ammunition Plant 1987). A single-base powder typically incorporates the use of organic solvents. Nitrocellulose of high- and low-nitrogen content are combined with volatile organic solvents, desired additives are blended with them, and the resulting mixture is shaped by extrusion and cut into specified lengths. The granules are screened to ensure consistency, and the solvents are removed. Various coatings, such as deterrents and graphite, are applied to the surface of the granules. The powder is dried and screened again, then blended to achieve homogeneity.
The manufacture of double-base powders requires the addition of nitroglycerine to the nitrocellulose. Two methods can be used. One method uses organic solvents, the other uses water. The organic solvent method mixes nitrocellulose and nitroglycerine with solvents and any desired additives to form a doughy mixture (Meyer 1987; National Research Council 1998; Radford Army Ammunition Plant 1987). The mixture is then pressed into blocks that can be fed into the extrusion press and cutting machine. The resulting granules are screened prior to solvent removal and the application of various coatings. The powder is dried, screened again, then blended to achieve homogeneity. The water method adds the nitroglycerine to a nitrocellulose water suspension to form a paste (Meyer 1987; Radford Army Ammunition Plant 1987). The water is removed by evaporation on hot rollers, then the dried powder is shaped by extrusion and cutting.
Triple-base powders use a solvent-based process similar to the double-base powder process (Meyer 1987; Radford Army Ammunition Plant 1987). Nitrocellulose and nitroglycerine are premixed with additives prior to the addition of a nitroguanidine solvent mixture. The nitroguanidine is incorporated into the overall mass without dissolving in the other materials. The final mixture is then extruded, cut, and dried.
The manufacture of smokeless ball powder requires a more specialized procedure (National Research Council 1998). Nitrocellulose, stabilizers, and solvents are blended into a dough, then extruded through a pelletizing plate and formed into spheres. The solvent is removed from the granules, and nitroglycerine is impregnated into the granules. The spheres are then coated with deterrents and flattened with rollers. Finally, an additional coating with graphite and flash suppressants is applied, and the batch is mixed to ensure homogeneity.
In the manufacturing process, smokeless powders are recycled and reworked (National Research Council 1998). When a powder within a batch is found to be unsatisfactory, it is removed and returned to the process for use in another lot. Manufacturers save money by recycling returns by distributors or the return of surplus or obsolete military powders. Hence, reworking and recycling the material assures good quality control of the final product, reduces costs by reusing materials, and reduces pollution by avoiding destruction by burning.
The production of smokeless powders is big business in the United States, where approximately 10 million pounds of commercial smokeless powders are produced each year. Most of the powder is sold to the original-equipment manufacturers to be used for manufacturing ammunition. A large amount is sold to domestic and foreign militaries (National Research Council 1998). The rest is sold in individual canisters (ranging from ½-pound cans to 12- or 20-pound kegs) to gun stores or hunting and shooting clubs for hunters and target shooters who prefer to hand load their own ammunition.
There are several ways smokeless powders are distributed within the United States (National Research Council 1998). Some manufacturers, foreign or domestic, produce, package, and sell their own powders commercially. They may also sell in bulk to resellers and to original-equipment manufacturers that repackage and sell it under their own labels. The powder manufacturers and repackagers may disburse large quantities of canister powders to distributors who later sell to smaller distributors and wholesalers, who in turn, supply cans to dealers, gun shops, shooting clubs, and other retailers. At this point, consumers can purchase a 1-pound canister of powder for approximately $15 to $20 from a retailer, though the cost per pound can be cheaper if bought by the keg or acquired through a gun club (National Research Council 1998).
Manufacturers who produce smokeless powders for the U.S. military can distribute it either by selling the powder directly to the military or by selling them the preloaded ammunition. Powders can also be shipped to U.S. military subcontractors, foreign governments, or foreign loading companies for loading into military ammunition (National Research Council 1998).
Improvised Explosive Devices
An explosion is the result of energy-releasing reactions, generally accompanied by the creation of heat and gases (a notable exception is thermites). A distinguishing characteristic of an explosion is the rate at which the reaction proceeds. There are low-order and high-order explosives, based on the speed at which the explosives decompose. In low-order explosives, the process of decomposition, called the speed of deflagration or burning, produces heat, light, and a subsonic pressure wave. (The reaction speed of the deflagrating material is less than the speed of sound.) In high-order explosives, decomposition occurs at the speed of detonation, creating a supersonic shock wave that causes a virtually instantaneous buildup of heat and gases. Table 1 shows some differences in low-order and high-order explosives (Bureau of Alcohol, Tobacco and Firearms 1994; National Research Council 1998; Saferstein 1998).
Table 1. Energetic Reactions
For low-order explosives, rapid deflagration causes the production of large volumes of expanding gases at the origin of the explosion. The heat energy from the explosion also causes the gases to expand. When the explosive charge is confined in a closed container, the sudden buildup of expanding pressure exerts high pressure on the container walls causing the container to stretch, balloon, then burst, releasing fragments of debris to nearby surroundings. It is this fragmented debris that produces the fatal result following the deflagration of an improvised explosive device (Saferstein 1998).
The safest and most powerful low-order explosive is smokeless powder. These powders decompose at rates up to 1,000 meters per second and produce a propelling action that makes them suitable for use in ammunition. However, the slower burning rate of smokeless powder should not be underestimated. The explosive power of smokeless powder is extremely dangerous when confined to a small container. In addition, certain smokeless powders with a high-nitroglycerine concentration can be induced to detonate. On the other hand, high-order explosives do not need containment to demonstrate their explosive effects (Saferstein 1998). These materials detonate at rates from 1,000 to 8,500 meters per second, producing a shock wave with an outward rush of gases at supersonic speeds. This effect proves to be more destructive than the fragmented debris.
The typical smokeless powder improvised explosive device, a pipe bomb, is roughly 10 inches long and 1 inch wide and contains approximately ½ pound of powder. The materials used for these devices are cheap and readily obtainable at commercial establishments. Smokeless powder is attractive for use in improvised explosive devices, because it is readily available and has the potential for a powerful explosion when the powder is placed in a closed container (National Research Council 1998). Larger explosive devices usually use bulk materials such as ammonium nitrate and fuel oil, typically purchased in greater quantity at an even cheaper price.
Many types of containers are used in the construction of smokeless powder bombs (National Research Council 1998). Whereas metal pipes are most common, plastic pipes, cans, CO2 cartridges, and glass or plastic bottles have been used. These containers are often placed within larger packages for ease of transport and concealment.
Another important part of the powder bomb is the initiation system, which provides the impetus to start the powder burning within its container (National Research Council 1998). A few examples include cigarettes, matches, and safety fuses (Scott 1994; Stoffel 1972). Improvised explosive devices utilizing smokeless powders within a robust container often include an initiation system, as shown in Figure 2 (Scott 1994).
Using data from the National Research Council on reported actual and attempted bombings using propellants during the five-year period from 1992-1996, Table 2 illustrates an average of 653 incidents per year involving the use of black and smokeless powders. Bombs containing black or smokeless powders were responsible for an average yearly count of about 10 deaths, 83 injuries, and almost $1 million in property damage for each of the five years. Using the National Research Council's data involving devices filled with black and smokeless powders, Table 3 illustrates the number of actual bombings that caused at least one death, one injury, or a minimum of $1,000 in property damage, as well as attempted bombings aimed at significant targets (National Research Council 1998).
Table 2. All Reported Actual and Attempted Bombings Using Propellants Between 1992 and 1996
Many methods for the analysis of smokeless powders have appeared over the years. These procedures have been extensively reviewed in a number of recent texts (Beveridge 1998; National Research Council 1998; Yinon and Zitrin 1993). The initial characterization of the powders is assessed using powder morphology and spot tests. Various instrumental analytical techniques allow organic additives such as nitroglycerine, diphenylamine, ethyl centralite, dinitrotoluene, and various phthalates to be detected and quantitated. These materials are usually analyzed using gas chromatography-mass spectrometry (Martz and Lasswell 1983) and liquid chromatography (Bender 1983; McCord and Bender 1998). illustrates the analysis of an IMR 700X powder using gradient high performance liquid chromatography (Wissinger and McCord 2002). More recently, methods involving capillary electrophoresis have also been shown to be effective (Northrop et al. 1991; Smith et al. 1999). Fourier transform infrared microscopy can be used for the identification of nitrocellulose (Zitrin 1998).
The process of manufacturing smokeless powders provides sources of inorganic ions that are present in postblast residue. These can be analyzed by ion chromatography. Although not unique to propellants, the presence of these ions can be used in forensic analysis to aid in the identification of the unknown powder. Potassium sulfate, sodium sulfate, potassium nitrate, barium nitrate, and other salts may be added during the processing of the powder. Nitrate, sulfate, hydrogen sulfide, chloride, and nitrite may appear as a result of the reactions for treating the cellulose to obtain nitrocellulose (Radford Army Ammunition Plant 1987). illustrates the analysis of H414 smokeless powder using ion chromatography. Also documented has been the presence of various cations found in the residue of smokeless powders after deflagration (Hall and McCord 1993; Miyauchi et al. 1998).
The wide variety of chemical components and the different morphologies of smokeless powders present a challenge for the forensic investigator. Physical characteristics of partially burned and unburned powder as well as the organic and inorganic materials that remain must be considered in the analysis of postblast residue. Although there are many techniques available for the determination of components in smokeless powder residue, the various formulations of powders make it necessary to continue the advancement of existing analyses and to develop new methods for testing the full range of available smokeless powders.
Bender, E. C. Analysis of low explosives. In: Forensic Investigation of Explosives. A. Beveridge, ed. Taylor and Francis, London, 1998, pp. 343-388.
Bender, E. C. Analysis of smokeless powders using UV/TEA detection. In: Proceedings of the International Symposium on the Analysis and Detection of Explosives. U.S. Government Printing Office, Washington, DC, 1983, pp. 309-320.
Beveridge, A., ed. Forensic Investigation of Explosives. Taylor and Francis, London, 1998.
Bureau of Alcohol, Tobacco and Firearms, Arson and Explosives Incidents Report (1994). ATF P3320.4, Department of the Treasury, Washington, DC, 1994.
Hall, K. E. and McCord, B. R. The analysis of mono- and divalent cations present in explosive residues using ion chromatography with conductivity detection, Journal of Forensic Sciences (1993) 38:928-934.
Martz, R. M. and Lasswell, L. D. Identification of smokeless powders and their residues by capillary column gas chromatography/mass spectrometry. In: Proceedings of the International Symposium on the Analysis and Detection of Explosives. U.S. Government Printing Office, Washington, DC, 1983, pp. 245-254.
McCord, B. and Bender, E. C. Chromatography of explosives. In: Forensic Investigation of Explosives. A. Beveridge, ed. Taylor and Francis, London, 1998, pp. 231-265.
Meyer, R. Explosives. 3rd rev., Weinheim, New York, 1987.
Miyauchi, H., Kumihashi, M., and Shibayama, T. The contribution of trace elements from smokeless powder to post-firing residues, Journal of Forensic Sciences (1998) 43:90-96.
National Research Council, Committee on Smokeless and Black Powder. Black and Smokeless Powders: Technologies for Finding Bombs and the Bomb Makers. National Academy Press, Washington, DC, 1998.
Northrop, D. M., Martire, D. E., and MacCrehan, W. A. Separation and identification of organic gunshot and explosive constituents by micellar electrokinetic capillary electrophoresis, Analytical Chemistry (1991) 63: 1038-1042.
Radford Army Ammunition Plant. Processing Manual. Radford, Virginia, 1987.
Saferstein, R. Criminalistics: An Introduction to Forensic Science. 6th ed., Prentice Hall, Upper Saddle River, New Jersey, 1998.
Scott, L. Pipe and Fire Bomb Designs: A Guide for Police Bomb Technicians. Paladin Press, Boulder, Colorado, 1994.
Selavka, C. M., Strobel, R. A., and Tontarski, R. E. Systematic identification of smokeless powders, an update. In: Proceedings of the Third Symposium on the Analysis and Detection of Explosives. Berghausen, Fraunhofer Institute fur Chemische Technologie, 1989, Chapter 3, pp. 1-27.
Smith, K. D., McCord, B. R., MacCrehan, W. A., Mount, K., and Rowe, W. F. Detection of smokeless powder residue on pipe bombs by micellar electrokinetic chromatography, Journal of Forensic Sciences (1999) 44:789-794.
Stoffel, J. Explosives and Homemade Bombs. Charles C. Thomas, Springfield, Illinois, 1972.
Wissinger, C. and McCord, B. R. A reversed phase HPLC procedure for smokeless powder comparison, Journal of Forensic Sciences (2002) 47:168-174.
Yinon, J. and Zitrin, S. Modern Methods and Applications in Analysis of Explosives. John Wiley, Chichester, United Kingdom, 1993.
Zitrin, S. Analysis of explosives by infrared spectrometry and mass spectrometry. In: Forensic Investigation of Explosives. A. Beveridge, ed. Taylor and Francis, London, 1998, pp. 267-314.
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