A qualitative comparison of smokeless powder measurements.

In the spring of 2000, the National Institute of Standards and Technology and nineteen participants conducted a comparison of smokeless powder additive compositional measurements. The purpose of this exercise was to determine the state-of-the-practice for forensic smokeless powder determinations. For the comparison, two handgun reloading powder samples were mixed and were compositionally evaluated for homogeneity by NIST. Participant laboratories included military, academic, and state/local, federal, and international forensic agencies. We solicited qualitative data identifying nitroglycerin, diphenylamine, N-nitrosodiphenylamine, and ethyl centralite. In addition, some laboratories provided identification of additional ingredients, such as nitrocellulose, or reported other measurements, such as dimensional morphology. In this paper, laboratory identification of the smokeless powder additives and a summary of the measurement methods used for the evaluations are presented. All laboratories correctly identified NG and the major stabilizers. Some disparity between laboratories was noted for the identification of minor (<0.01% by weight) stabilizers and stabilizer decomposition products.