Firearms P2 Flashcards
How do we identify a firearm?
Type of firearm
Name/manufacturer
Model number
Caliber
Serial Number
What is required by federal law to be on a firearm?
Name and location of manufacturer
Model number
Caliber
Serial Number
Trigger pull
amount of force required to move the trigger back far enough to release the sear and discharge the firearm
as the finger is placed farther towards the end of the trigger (power arm), ________ will be required to pull the trigger
less force
the trigger becomes ______ to pull as the finger is placed closer to the pivoting point (fulcrum)
harder
power arm
end of the trigger
fulcrum
pivoting point of the trigger
mechanical advantage
distance the finger is away from the pivot point
Trigger pull methods
weights
spring gauge
computer-based trigger determination
surface preparation
polishing the damaged surface to a shiny, mirror-like finish, and removing any grease or dirt
magnetic method
a strong magnet is placed behind the firearm, and fine magnetic dust is sprayed over it
chemical etching
apply the chemical, let it sit for a few minutes before washing it off and viewing the serial number, then repeating until it is visible
electrochemical
increases metal oxidation of the metal is d with an electric current
the most important factor is the _______ left behind on the bullet or cartridge case
clarity of marks
IBIS
Integrated Ballistics Identification System, used to help link bullet and cartridge case evidence from one crime to another
How is IBIS used?
Digital images are taken of the evidence and stored on the database, which is linked through the National Integrated Ballistics Information Network (NIBIN). These digital images are given a signature which can be compared to other images representing bullets or cartridge cases within the same class
What do sticky stubs do?
Collect metallic primer residues
What does sodium rhodizonate do?
Tests for lead
What does griess do?
Tests for nitrates in gunpowder
Chamber
Area at the rear of the barrel that houses a cartridge during firing
Breech
Rear wall of the chamber
Firing pin
Forcefully strikes cartridge, igniting it
Trigger
Lever that is pulled to release the firing pin
Rifled barrels
Fires BULLETS
Interior has spiraled lands and grooves
Width of the barrel is called the bore
Smooth barrels
Fires SHOTS or SLUGS
Width of barrel is the gauge
Shotgun characteristics
Smooth barrel
Two part stock
Slide/bolt/pump action
Rifle characteristics
Rifled barrel
Two part stock
Slide/bolt action
Pistol characteristics
Rifled barrel
One part grip
Slide/bolt action
Revolver characteristics
Rifled barrel
One part grip
Cylinder action
Components of a cartridge
Case
Primer
Propellant (powder)
Projectile (bullet)
Bullets have a ____ core
Lead
The smaller the shot number, the
Larger the shot
Components of a shell
Shot
Wad
Powder
Primer
Hull/Case
Calvin Goddard
US army colonel/physician who developed the comparison microscope
When creating exemplars, bullets are fired into
Water, soft rubber, graphite, or soft fibers
What information do headstamps typically contain?
Size
Cartridge descriptor
Manufacturer
Comparison process
Place cases or bullets on stages
Line up corresponding marks
Photograph
Count CMS
You find primer residues at what distance?
Less than 10m
Which test do you use to identify bullet holes in clothing?
Sodium rhodizonate test
The SEM detects what
Primer residue
When attempting to recover serial numbers, why do we use acids for recovery?
Acids attack the denser metal under the serial number more slowly than the metal surrounding the number
What shape impression does the firing pin make?
Round shape
What does the breech face do to a cartridge
Presses against cartridge and leaves lines
What do you submit to NIBIN
photos of breechface, firing pin, ejector and land marking on test fired bullet
