Breech Face
Definition
The forward surface of the bolt, slide, or breech block that seals the chamber and contacts the cartridge case head during firing. Its surface topography is impressed into the case head under propellant gas pressure.
- Primary contact point
- The cartridge case head. Pressure during firing presses it against the breech face.
- Material marked
- Soft brass case heads receive clear impressions from the breech face topography.
- Marking type
- Machining striations and surface topography emboss onto the case as individual characteristics.
Common questions
What is the breech face and where is it located?+
The breech face is the flat metal surface at the rear of a firearm's chamber. It's part of the bolt, slide, or breech block that seals the chamber and makes direct contact with the cartridge case head during firing.
Why is the breech face important in ballistics analysis?+
When a round fires, the cartridge case head is pressed hard against the breech face under propellant gas pressure. The surface topography of the breech face leaves distinctive impressions on the soft brass case head. These machining striations and marks create a unique signature that can link a cartridge case back to the specific firearm that fired it.
How does the breech face create evidence?+
The breech face's imperfections and scratches emboss onto the cartridge case during firing, creating a reproducible pattern. Since no two firearms have identical breech face topography, these marks become a reliable identifier for matching cases to guns in casework.
Related terms
- AFTE Conclusion Scale
- Association of Firearm and Tool Mark Examiners scale: identification, inconclusive (subdivided A, B, C), elimination, unsuitable. The court-admissible vocabulary.
- 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...
- Class Characteristics
- Features deliberately or systematically imparted to a group of items by design or manufacture, such as the calibre of a bullet, the...
- Comparison Microscope
- Two compound microscope bodies connected by an optical bridge that presents one half of each body's image in a single split eyepiece...
- 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....
- 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...
- IBIS / NIBIN
- Integrated Ballistic Identification System (Forensic Technology Inc., Canada) and Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF)'s National Integrated Ballistic Information Network....
- Individual Characteristics
- Surface features on a fired bullet or cartridge case that arise from random or unique events (tool wear, corrosion, service damage) and...
- 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...
Explained in these topics
- Cartridge-Case Markers: Firing Pin, Breech Face, Ejector and ExtractorThe forward surface of the bolt, slide, or breech block that seals the chamber and contacts the cartridge case head during firing. Its surface topography is im...
- Forensic Examination of Firearms, Bullets, Shells and CartridgesThe flat metal surface at the rear of the chamber that the case head slams against on firing. Machining striations on the breech face emboss onto the soft bras...