Gear Code Extraction from Microstamped Cartridges
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The firing pins of three different handguns were modified to stamp a six-digit alpha-numeric code and a circumferential digital code known as a gear code into the primer of a cartridge when fired. In this paper the transfer of gear codes from firing pin to primers was evaluated using scanning electron microscopy (SEM). Only those cartridges that received poor clarity marks optically as regarding the alpha-numeric code were chosen for evaluation in the SEM. Photo editing software was employed to clearly outline and decipher the gear code around the circumference of the microstamped primer. Results show that the better imaging of the SEM allows more of the alpha-numeric identifiers to be distinguished as well as more of the gear code structure, however complete recognition is still not possible in all cases.
This article is published as T. Grieve, L.S. Chumbley, J. Kreiser, T. Lizotte, O. Ohar, “Gear Code Extraction from Microstamped Cartridges,” AFTE Journal (Winter 2013) 45, pp. 64-74. Posted with permission.