Forensic Ballistics
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What are the different types of guns?
-Self loading Pistol - revolver -Shotgun -Rifle
What is the difference between rimfire and centerfire?
Rimfire refers to a firearm cartridge that has its priming compound located in a ‘rim’ around the base of the cartridge casing. Centerfire cartridges have an external pocket in the base where the primer is inserted.
What type of gun is a GFL 9mm Luger for?
Pistol
What type of gun is a Magtech .88 special-short for?
Revolver
What is the difference in ammunition for pistols and revolvers?
Pistol cartridges have a groove at the base that allows it to be ejected easily. Revolver cartridges have a larger base so that they are held in the cylinder.
What is the most common gauge for a shotgun?
12-gauge
What does calibre mean ?
It’s a unit of measure indicating the diameter of a gun barrel and the diameter of the gun’s ammunition
What is the bore?
The interior of the barrel of a firearm
What is the cartridge case?
It houses the bullet, primer and propellant
What is the primer?
The gun’s firing pin strikes the base of the cartridge and friction the cause ignition of the percussion primer
What is the propellant?
Chemicals that burn to create high pressure that forces projectile along barrel
After the primer has ignited the propellant what happens to the bullet?
hot gas is produced which expels the bullet
What is gun shot residue?
Any particle/ residue from the primer and propellant that are deposited on surfaces close to the gun
Why is primer residue more useful than propellant residue?
The chemical structure isn’t found in the general environment
What are the primary ways of acquiring gun shot residue?
-firing a gun -Standing close to a gun when its fired
What are the secondary ways of acquiring gun shot residue ?
-handing a recently fired gun or spent cartridge case -physical contact with someone who is contaminated
How much GSR is transferred each time it comes into contact with someone?
10%
How far does gunshot residue from a handgun travel ?
3m
What does primer gunshot residue contain?
Lead, barium, antimony and often other elements
How is primer GSR analyzed?
SEM- highly magnified images and chemical analysis
What does it mean for primer GSR to be highly characteristic ?
That it’s not produced by anything else other than guns/ firearms origin
What are advantages of primer GSR?
-recovered from surfaces using adhesive tapes -Does not chemically degrade
What is the composition of primers?
-explosive -oxidizer -sensitizer -frictionator -fuel -binders
What is an oxidizer?
Produces oxygen to enable combustion