Ammunition is most often comprised of a lead-based priming mixture which contributes to the traditional characteristics of gunshot residue (GSR). Due to the health risks often associated with lead, lead-free primer alternatives are becoming increasingly more popular. Thus, it is becoming more difficult to determine the presence of GSR based on traditional means, i.e. the presence of lead (Pb), barium (Ba), and antimony (Sb). Eight different ammunitions were purchased which consisted of one lead-based and one lead-free from four different manufacturers, including Winchester, Federal, Liberty, and Sellier & Bellot. Half of the rounds from each manufacturer and chemical composition (i.e. lead-based or lead-free) were disassembled, e.g. the projectile and smokeless powder were removed, leaving the priming cup in place (i.e. primed only). The remaining cartridges were left intact (i.e. full cartridge). Both the full cartridges and the primed only cartridges for each ammunition were fired using a 9mm Glock and the cartridges were collected post-fire, and subsequently deprimed. Five cups and five anvils from each type of ammunition were adhered to aluminum stubs via colloidal graphite. The GSR remaining on the anvils and in the cups was then analyzed using scanning electron microscopy coupled with energy dispersive x-ray spectrometry (SEM-EDX). Three spectra were collected for each anvil and each cup resulting in 30 total spectra per type of ammunition. The primary element peaks were then selected and four different dataset matrices were created for the full cartridge anvils, full cartridge cups, primed only anvils, and primed only cups. The data was processed using unit vector normalization and was then analyzed using principal component analysis (PCA) and linear discriminant analysis (LDA) to determine the characterization between lead-free and lead-based ammunition. The anvils provided better separation and characterization based on the ability to better collect x-rays, and therefore demonstrated the capability of the ammunition to cluster by both primer mixture composition and manufacturer. The lead-based and lead-free primers showed consistencies across samples, such as the presence or absence of K, which allowed for characterization based on primer composition.
Master of Science (M.S.)
College of Sciences
Forensic Science; Forensic Analysis
Length of Campus-only Access
Masters Thesis (Open Access)
Terry, Molly, "Characterization of Post-Fire Priming Cup Residue Using Scanning Electron Microscopy Coupled With Energy Dispersive X-Ray Spectrometry" (2016). Electronic Theses and Dissertations. 5258.