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Study of firearms and bullets:Bullets and Cartridges:Named by caliberCaliber – measure of the diameter of a cartridge and the barrel of the gunDown to the hundredth of an inch: ex: .22, .45European firearms are metric – ex: 9 mmBullet – projectile which exits the barrel of the gunVary in shape and materialHundreds of typesMost are variations of three shapes and materialsShapes – round, hollow and wadcutterFirearm types:Handguns – able to be fired by one handRevolver – separate from chamber and 6 cartridges in the cylinderPistol – cartridge is part of the chamberSemiautomatic – up to 10 cartridges – fires 1 bullet per pullAutomatic – fires until empty with one trigger pullLong guns – Shoulder arms: (require 2 hands)Rifle – single bulletShotgun – cartridge with multiple pelletsFires small lead balls or pellets held in a shotgun shellThe gauge is the diameter of the barrel. The higher the bumber the smaller the barrelMachine gun – continuously firesWhat makes them unique:Each type of firearm has a unique pattern to the barrel – this cause lands and grooves that are INDIVIDUAL to each firearm.Lands – raised areas of the barrelGrooves – valleys (recessed areas) of the barrelThe grooves guide the bullet through the barrel which keeps it straight and causes a pattern on the bullet.These are the identifiable marksBullets – made of alloys of lead, copper, brass, bronze & steelMany shapes within each caliberMade of: a projectile, primer, gunpowder, The primer ignites the gunpower – propelling the bulletFiring pin – the firing pin make a unique mark on each individual casing. This also is almost impossible to recreate.Because of the uniqueness of the lands and grooves – using microscopes – Forensic scientists can accurately match the striations of bullets. It is impossible to have 2 identical barrels.The NIBIN – The FBI houses a National Integrated Ballistic Network that has a index of markings.Gunshot residue: Composed of unburned powder carried sideways from the firearmNitrates from the GSR stick to the person holding the firearmWhen a Bullet hits a target – three things can happen:They mushroomThey disintegrateThey go clean through and lodge in something else.How trajectory is calculated:Where a bullet is fired from is called the trajectory.Find 2 reference points along the flight path of the bulletAssume they travel in a straight line (no gravity)A fired bullet has 2 forces Forward force from gunpowderDownward force of gravityBegins to drop as soon as it leaves the barrelShooter must make adjustments for thisWind speed and direction is crucialBALLISTICS:Three major areas of ballistics:Interior ballistics – study of projectiles within the firearmExterior ballistics – study of projectiles in flightTerminal ballistics – study of projectiles interactions with a targetWound ballistics – dealing with the human bodyMajor Issues when dealing with the Forensics of Ballistics:RangePositionLocation of victimNumber of shots firedSequence of shotsAny type of material between the firearm and victimHow this is all figured out.Kinetic Energy – the greater the mass the greater the energyThe greater the speed the greater the energySmall fast bullets can cause more damage than large slow ones.Here is a cool website to figure this out: Damage Depends on the bullet and size of the gunDistance from the bodyLocation and path/trajectory of injury ................
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