A Comparison of Ballistic Impressions on Cartridge Case (image) National Institute of Standards and Technology (NIST) Share Print E-Mail Caption Typical results for a comparison of breech face impressions on cartridge case primers, using the NIST technique known as Congruent Matching Cells, or CMC. In pair A, almost all the cells from the first image match cells from the second image, indicating that the two cartridge cases were likely fired by the same gun. In pair B, some cells find similar cells, but they are randomly distributed, and therefore, not considered matching. Only the area of interest for each primer is shown. Portions of the primer surface that were not compared appear in white. The color scale indicates relative surface height in micrometers. Credit Credit: Johannes Soons/NIST Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.