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Examination of Firearms (Cycle-of-Fire Steps (Step 5: Obturation - A…
Examination of Firearms
Cycle-of-Fire Steps
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Step 4: Firing - The action of pulling the trigger which causes the firing pin to strike at the cartridge
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Step 3: Locking - The action of the breech bolt locking the cartridge into the correct posiiton within the barrel
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Step: Feeding - The action of placing a cartrdige into the chamber and the brech bolt pushes it into its final position
Examination
Trigger Pull - The methods used to determine trigger pull include trigger weights, spring scale, and a digital scale
Safety Features - There are number of rules to follow to ensure the safety of the examiner. Some of which include holding the firearm in a safe direction, keeping it unloaded, but handling it as if it were loaded, etc.
Long Guns - Examination involves determining the magazine capacity, its abilty to be full automatic, find a selector switch, and test firing
Test Firing - Some of the processes done while test firing include testing the firearm's ability to function properly, the recovery of the bullet, and any other testing done on automatics, single action and double actions
Single and Multi-barreled Pistols - Examining involves determining the capacity, test firing, and testing safety features
Drop Testing - These tests are performed in cases in which a firearm had been fired after being dropped
Autoloading Pistols - Examination involves inspecting the magazine capacitance with the use of a dummy cartridge to determine where it is capable of being a full automatic
Shock Test - A similar test to the drop test however, a hammer is used to hit the firearm to test whether or not it will missfire
Revolvers - Examination involves removing and inspecting the interior of the cylinder for any damage, cocking the hammer, and test firing
Evidence Receipt - Any time an examiner comes in contact with a piece of evidence to perform any testing, proper documentation must be filled out to ensure a complete and unbroken chain of custody
Firearm Identification
Military Firearms - Firearms used in the military are typically more difficult to identify due to the lack of identification information that are listed on regular firearms
Proof Marks - Foreign firearms do not typically list the manufacture but rather a location. In which case, an examiner will look at proof marks for identification
Handguns
Double-Action Revolvers - These revolvers only require that the trigger be pulled to cock the hammer
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Single-Action Revolvers - The hammer on these revolvers need to be cocked manually for there to be enough pressure for firing. The action of cocking the hammer also moves the revolving chamber
Full Autonomic Pistols - No manual action is requred. Once the trigger is pulled, it automatically causes a cartridge to feed through, fire, extract, eject, and repeat the cycle
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Conrad, William. “Module 08 :: Examination of Firearms” Firearm Examiner Training, projects.nfstc.org/firearms/.