Firing-Pin Impression
Definition
The indentation left in the primer cup by the firing-pin tip at the moment of discharge. Its shape (circular, oval, rectangular), size, and individual surface texture are comparison features.
- Location
- Primer cup of a fired cartridge case
- Cause
- Firing-pin tip striking the primer at discharge
- Shape classes
- Circular, oval, rectangular
- Comparison value
- Class shape plus individual surface texture
Common questions
How does the firing-pin impression differ from the breech-face mark on the same case?+
The firing-pin impression is a localised dent at the primer's centre caused by the pin striking it, while the breech-face mark is a broader impression across the case head left by the surface the case slams back against under recoil. Examiners use both together, not interchangeably.
Can firing-pin shape alone identify a specific weapon?+
Shape only narrows the field to a class of firearms sharing that pin design. Individualisation to one specific weapon requires the finer, randomly acquired surface texture of the pin tip, compared under magnification against test-fired exemplars from the suspect weapon.
Related terms
- AFTE Theory of Identification
- The Association of Firearm and Tool Mark Examiners' standard (1992, revised 2011) for reporting tool-mark comparison conclusions as Identification, Inconclusive, or Elimination...
- Breech Face
- The forward surface of the bolt, slide, or breech block that seals the chamber and contacts the cartridge case head during firing....
- Ejector Mark
- A striated or impressed feature left on the cartridge case rim or base by the ejector pin at the moment of case...
- Extractor Mark
- Striations or impressed features on the extractor groove of the cartridge case, produced by the spring-loaded extractor claw during the extraction stroke....
- Headstamp
- The manufacturer identification and calibre marking stamped into the base of a cartridge case during manufacture. Includes manufacturer codes, year, NATO cross...
- IBIS BrassTRAX-3D HD
- Forensic Technology's automated ballistic correlation system for cartridge cases. Captures topographic maps of the breech-face, firing-pin, and ejector areas and ranks case-to-case...
- Magazine-Lip Marks
- Parallel striated marks on the cartridge case below the extractor groove, produced by the magazine lips as the cartridge is stripped from...
- NABIS
- National Ballistics Intelligence Service; the UK police intelligence service that maintains a national headstamp and firearm reference collection and coordinates ballistic intelligence...
- NIBIN
- National Integrated Ballistic Information Network. ATF-operated distributed network of IBIS acquisition sites and correlation servers across the United States, active since 1999...