Thus, zinc (Zn) and titanium (Ti) would be found in residue. Antimony define free#Heavy metal (lead) free primers can have zinc peroxide, titanium powder, tetrazene, diazonitrophenol, and nitrocellulose. A commonly used lead-based primer contains the shock sensitive explosive lead styphnate, oxidizer barium nitrate, and antimony sulfide fuel, yielding residue metals lead (Pb), barium (Ba), and antimony (Sb). Residues often derive from the primer cap mixture of components including an explosive, oxidizer, fuel, frictionator, sensitizer, and binder. Residues can be either inorganic or organic in nature. This residue, called gunshot residue (GSR), can consist of both burned and unburned primer or powder components, combined with additional residue from the surface of the bullet, surface of the cartridge case, and lubricants used on the firearm. (Pun and Gallusser, 2007) Composition of Gunshot Residueįiring a weapon produces combustion of both the primer and powder of the cartridge, creating an expanding plume of gas with smoke containing the residues of combustion. Unburned gunpowders can have recognizable shapes, colors, and sizes of grains. Progressive burning: gunpowder grains that are multiperforated and rosettes that have a burning surface area that increases continuously as the grains are consumed. Neutral burning: gunpowder grains that are single perforated and the burning surface area remains relatively constant. The burning rate of gunpowder can be classified in three categories:ĭegressive (regressive) burning: gunpowder grains formed in flakes, balls, and sticks have a burning surface area that decreases continuously as the grains are consumed. In an explosion something gets very big very fast. Return to Criminalistics Laboratory Methods.įirearms Tutorial menu Examination of Gunshot Residue Appearances of GunpowderĪll gunpowders are designed to burn quickly to produce rapid expansion of gas in a confined space.
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