Extractor Mark
Definition
Striations or impressed features on the extractor groove of the cartridge case, produced by the spring-loaded extractor claw during the extraction stroke. Typically at the 3 o'clock position opposite the ejector mark.
- Location
- Extractor groove of the cartridge case
- Cause
- Spring-loaded extractor claw during the extraction stroke
- Typical position
- 3 o'clock, opposite the ejector mark
- Field
- Firearms and toolmark examination
Common questions
Why is the extractor mark useful for individualising a cartridge case to a specific firearm?+
The extractor claw develops microscopic wear and manufacturing imperfections unique to that individual mechanism, impressed into the brass as consistent, reproducible striations, letting an examiner compare marks on a questioned case against test fires from a specific firearm.
Why is the extractor mark's position relative to the ejector mark useful?+
Both marks form at fixed points in the action's mechanical cycle for a given firearm design, so their relative clock positions on the case head are consistent for that make and model, which helps narrow the class of firearm even before individual striation comparison.
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...
- Firing-Pin Impression
- The indentation left in the primer cup by the firing-pin tip at the moment of discharge. Its shape (circular, oval, rectangular), size,...
- 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...