Which mark is a region of interest on a fired cartridge?

• A. Headstamp
• B. Rim thickness
• C. Breech face marks
• D. Primer deposit

Answer: (C)

When a cartridge is fired, the firearm leaves distinctive impressions on the cartridge case from components that contact it. The breech face, the surface that closes against the cartridge in the chamber, presses into the base around the primer and creates unique marks that reflect that particular gun’s machining and wear. These breech face marks form a pattern that can be compared to test fires from a suspected firearm to determine a match, making them the region of interest for identification.

Headstamps are manufacturer markings on the base and aren’t produced by the firing event. Rim thickness is a physical dimension of the case, not a marks pattern left by the firearm. Primer deposit is residual chemical material, not a firearm-imprinted pattern used for linking a cartridge to a gun.