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BALLISTICS and FIREARMS. “ A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed.” 2 nd Amendment to the US Constitution.
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“ A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed.” • 2nd Amendment to the US Constitution
“Studies have shown that no two firearms, even those of the same make and model, will produce the same unique marks on fired bullets and cartridge cases. ”
“Manufacturing processes, use, and abuse leave surface characteristics within the firearm that cannot be exactly reproduced in other firearms. “ Taken from Firearms ID .com
Two general classifications of firearms: Handguns (side arms) Rifles (shoulder weapons)
These weapons are rarely examined by a criminalist as they are found in military zones.
The barrel or bore of the gun is the conduit through which the cartridge will pass. One type of cartridge holds many round balls of lead or steel called ‘shot’.
Databases on the patterns of spiraling grooves kept by FBI Bureau of Alcohol, Tobacco and Firearms (ATF) Spacing and direction (clockwise or counterclockwise) of the lands and grooves on a slug along with caliber… Examiner knows exactly what brand of weapon
The Magnus effect is the phenomenon whereby a spinning object flying in a fluid creates a whirlpool of fluid around itself, and experiences a force perpendicular to the line of motion. Wikipedia (knuckleball)
The cartridge is plastic, with shot, propellant, and primer. Wads are pieces of paper, cardboard or cotton to keep materials from mixing.
The primer is lit mechanically when struck by the firing pin. Primer ignites, burns, fast and hot Sets off the propellant which Pushes the shot out of the barrel SHOTGUN!
Not all firearms eject spent cartridges But all eject gun shot residue GSR GSR contains specific chemicals: lead, barium and antimony, the material of primer mixtures GSR shows metal content and manufacturers use metal additives in known proportions
The other type of ammunition has a single , solid projectile in a cartridge. The cartridge case is called a ‘jacket’ surrounding a metal core called the ‘slug’.
A modern cartridge consists of the following:1. the bullet itself, which serves as the projectile;2. the case, which holds all parts together;3. the propellant, for example gunpowder or cordite;4. the rim, part of the casing used for loading;5. the primer, which ignites the propellant.
Forces cause the projectile , the slug, out the open end • of the barrel. • Energy is required to throw a slug which produces • noise and heat, which deforms the metals of the slugs.
A gun with spiral marks in it, is ‘rifled’. The spirals on the inside of the barrel, the bore, cause the slug to spin, keeping it traveling on a straight course.
Shoulder weapons with this rifling were called ‘rifles’ Handguns and rifles have the rifling. Shotguns do not.
rifle bullet samples handgun bullet samples
The heated slug spins along the rifling inside the barrel and picks up the riflings, impressions. Slug recovered at crime scene, will bear same markings on it cartridge as found on the inside of bore only reverse of … Lands are raised areas and grooves are depressions on the metal Slugs deform as they hit objects.
Gauge and Caliber Of Ammunition
Gauge Measure of shotguns only; shot to an equivalent slug 12 gauge shotgun packs a load equivalent to a solid lead slug weighing 1/12 of a pound 10 gauge; load weighing 1/10 of a pound Higher # ,lighter the load
Caliber is measure of bore of weapons; handguns and rifles Measure in 1/100ths of an inch. .45 caliber handgun bore is 45/100 of 1 inch. Magnum is not a caliber but a description of firepower of propellant. 44 magnum and 45 caliber weapons and ammunition are not interchangeable… different propellant
9 mm caliber is a metric measurement. Originally made by European gun manufacturers. Measures the caliber of a gun in mm not inches.
FBI, ATF (Alcohol, Tobacco and Firearms) Government agencies established databases of patterns of grooves in guns. Lands and grooves on gun, match lands and grooves on gun and evidence is individualistic for a gun. Can also tell manufacturer, type, size of gun
Valuable forensic evidence • Firing pin marks on the breach face of the cartridge reveals specific markings to a particular gun • Where cartridge lands, is left… where is shooter?
Not all firearms eject cartridges.. All eject gunshot residue (GSR) vapor, particulates, heated chemicals, lead barium, antimony If found on suspect means: -they fired weapon -were present when fired or -handled a recently fired weapon Individual ammunitions composition varies with manufacturer… Can trace ammo or batches of ammo
In the field of forensic science, forensic ballistics is the science of analyzing firearm usage in crimes.
THERE IS A METHOD TO THE MADNESS…. Energy CalculatorExample: The muzzle energy of a 300 Remington Ultra Mag 180gr Core-Lokt Ultra bullet propelled at 3250 feet per second is determined using the follow formula:M x V2 ÷ 450400 = foot pounds energy. Step 1: Multiply M (M = bullet weight in grains) times V2 (V2 = the square of bullet velocity in feet per second): 180 x 3250 x 3250 = 1,901,250,000 Step 2: Divide the product of step 1 by 450400: 1,901,250,000 ÷ 450400 = 4221 foot pounds of energy.
Gun powder and particles residue indicates proximity to victim and angle of entry wound.
Armor piercing shell of the APBC1 Light weight ballistic cap2 Steel alloy piercing shell3 Desensitized bursting charge (TNT, Trinitrophenol, RDX...)4Fuse (set with delay to explode inside the target)5Bourrelet (front) and driving band (rear)
