Ballistics Flashcards
What are the 3 study areas of ballistics?
- Internal ballistics
- External ballistics
- Terminal/wound ballistics
What is ballistics?
The science if travel of a projectile in flight
What is internal ballistics?
The approximately 2ms timespan between the impact of the firing pin/striker and the exit of the projectile, the time when the projectile receives the characteristic markings that may be linked to the firing weapon
What is external ballistics?
The flight of the projectile after leaving the barrel - bullet trajectory, gunshot residue patterns and distance determination are made in this phase
What is terminal/wound ballistics?
What takes place when the projectile strikes the target - enters ve and exit wounds, bullet wipe
What is bullet wipe?
The material deposited by the bullet on its target or any structure it may contact during its flight
What are the characteristics of bullet wipe?
- may be derbis from the barrel collected by the bullet
- composed of soot, lubricant and particles of primer and metal fragments
- may be present when no GSR can be detected
What is a hand gun?
Short barrelled firearm (has a rifled barrel)
What is the sight?
Device used to assist the alignment/aiming of the weapon
What is the barrel?
Tube through which the projectile is propelled at high velocity, can be smooth or grooved
What is the muzzle?
End of the barrel that the projectile exits from
What is the hammer?
When the trigger is pulled, the hammer swings to impact the primer and initiate firing
What is the trigger?
Mechanism that activates the firing sequence of a firearm
What are the 3 broad categories of firearms?
- Rifle
- Shotgun
- Handgun
What are the different action types of firearms?
- single shot
- repeating
- self loading
- fully automatic
What is a rifled barrel?
A barrel with helical grooves cut lengthwise into the inside of the barrel which causes the bullet to spin along its axis upon exit from the barrel
What does the spin in a rifled barrel do?
Serves to gyroscopically stabilise the projectile and improve aerodynamic stability and accuracy
Which types of firearms have rifled barrels?
Rifle and handgun
What is a rifle?
Shoulder weapon with a grooved barrel, initially a single shot weapon
What is a handgun?
- firearm with a shorter barrel - gun is designed to be shot with 1 or 2 hands
- designed to fire batches of small projectiles
- target a wide area but don’t travel long distances
What is a projectile?
Any object propelled by the exertion of force
What are the components of a cartridge?
- case: generally brass, nickel or steel
- primer: an ignition for the propellant
- powder: propellant (gunpowder)
- bullet: solid projectile that leaves the firearm
What are the 2 main locations of primer?
Centre and rim
What is rimfire ammunition?
The firing pin will strike the rim at the end of the cartridge which ignites the internal primer
What is centrefire ammunition?
The primer is installed in a small gap in the centre of the base, requires a much stronger firing pin to strike
What is callibre?
- the approximate interna diameter of the barrel, measured between the lands of a rifled barrel
- the larger the number, the wider the barrel
What is gauge?
- the unit of measurement for bore diameter, based on how many rounds you could make for the gun with 1 pound of lead
- the smaller the number, the wider the barrel
What is weapon examination based on?
- gunshot residue
- cartridge cases
- bullet fragments
- rifling patterns
A gunshot wound to the skull will be beveled in the direction….
That the projectile travelled
What is weapon examination based on?
- gunshot residue
- cartridge cases
- bullet fragments
- rifling patterns
What are the different types of shell casing characteristics?
- beech markings
- firing pin marks
- extracting pin marks
- ejector marks
What are the characteristics of striations?
- number of groove or land impressions
- direction of twist
- measure of the rifling impression
What is muzzle energy?
Kinetic energy as a bullet is expelled from a firearm
What are the forces that act on a projectile?
Gravity: downward acceleration (bullet drop)
Drag: air resistance
Wind: deviates projectile from trajectory
How can the distance between the gun and victims be estimated?
Looking at gunshot residue patterns
Long distance
No GSR on victim
Close-range
GSR on victim: spread out
Near-contact
GSR on victim : concentrated circle
Contact shot
“Blown out” entrance wound
What is the permanent cavity?
The track made by the diameter of the bullet
What is the temporary cavity?
Pressure wave caused by the bullet (higher velocity, larger the size)
Exit wounds are ……… than enterance wounds
Larger
What is GSR analysed with?
SEM and X-ray analyser
What is GSR analysed for?
- trace amounts of lead, barium and antimony
- elements such as aluminium, silicon, Sulfur potassium and calcium
What is wound ballistics?
The medical effects of projectiles on humans
What is penetrating trauma?
Injury when an object pierces the skin
What is GSR?
- the burned and unburned primer and propellant particles which are deposited as a cloud of material expelled from the barrel after firing
- GSR particles form as a result of rapid cooling of the discharge gases and solid matter
