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Module 8: Examination of Firearms (Firearm Evidence (identification…
Module 8: Examination of Firearms
Cycle of Fire Steps
steps 1-5
feeding
insertion of cartridges into the chamber
locking
the breech bolt mechanism locks the cartridge into position in the barrel before firing
firing
when the breech is fully locked, a pull on the trigger mechanically translates to the firing pin release
obturation
occurs when powder gases under high pressure are sealed to prevent them from jetting between primer cup and cartridge case, cartridge case and primer wall, and projectile and bore
chambering
insertion of the cartridge into the chamber
steps 6-9
unlocking
the reverse of the locking process and is frequently performed in conjunction with extraction
extraction
the removal of a case from a chamber must begin with slow movement that can be accelerated as soon as the case loosens from the chamber
ejection
the cartridge case encounters a projection that is usually at right angles to the exit portal of the breech
cocking
the hammer string is usually cocked when the bolt of a rifle, pistol, or repeater shotgun is retracted
can be traced in the firing of an breechloading weapon
Firearm Evidence
evidence receipt
each firearm recovered should be properly packaged and accompanied by documentation
details of the incident
examinations requested
examination documentation
must be complete and accurate
a worksheet should be completed per lab protocol
copies of examiner's research should be included in case folder
identification information
brand name or trademark
serial number
model designation
caliber designation
importer, if applicable
should be marked according to lab protocol prior to conducting any examinations