- 01: Introduction
- 02: History
- 03: Propellants, Firearms, and Ammunition Development
- 04: Modern Firearms Manufacture
- 05: Small Arms Ammunition
- 06: Evidence Handling Procedures
- 07: Equipment and Instrumentation
- 08: Examination of Firearms
- 09: Cartridge and Shotshell Examination
- 10: Characterization and Evaluation of Fired Projectiles
- 11: Bullet Comparison and Identification
- 12: Gunshot Residue and Distance Determination
- 13: Toolmark Identification
- 14: Communicating Results
- Resources
Steps 6-9
Home > Examination of Firearms > Steps 6-9
Step 6: Unlocking
This is the reverse of the locking process and is frequently performed in conjunction with extraction.
Step 7: Extraction
Although cartridge cases do not commonly exceed their elastic limit during firing, they have a tendency to stick to the chamber after firing. After firing, cartridge cases are larger in diameter than before firing. If the fired cartridge case is intended for reloading, it must be full‑length resized in a reloading die.
The removal of a case from the chamber must begin with a slow movement that can be accelerated as soon as the case loosens from the chamber. This slow‑to-fast action can be demonstrated by carefully observing the extraction process in a high‑velocity bolt-action rifle.
All cartridge cases are designed with a rim or groove (cannelure) at the base so that an extractor claw can grasp this edge in order to achieve extraction.
Step 8: Ejection
In the final stages of extraction, the cartridge case encounters a projection that is usually at right angles to the exit portal of the breech. Rotating on the fulcrum of the extractor, the case base is contacted on the opposite side by the ejector, which flips the case out of the actuating mechanism.
Step 9: Cocking
The hammer spring is usually cocked when the bolt of a rifle, pistol, or repeater shotgun is retracted. An exception to this is the M1917 Enfield Rifle, which cocks upon forward motion of the bolt. Exposed hammers may be cocked by manual retraction, using the thumb. The Walther series of pistols provides for manual cocking or trigger pull cocking (double action), as do most open hammer revolvers.
Click here to watch a video on steps 6-9 of the cycle of fire.
