Who Did The Shooting? Wonderful article from 1927 showcasing the then new science of forensic ballistics.Full description
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Descripción: Introduccion
Homeschool Forensic Science Unit Study
(from Perry-Systems.com )
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Ballistics
Forensic Science II
Ballistics
Machinegun Barbie meets Benny “the chimp” Gambino
Ballistics the study of projectiles, trajectories, and the effect on the target
Internal ballistics
External ballistics
What happens in the weapon
What happens after the bullet leaves the barrel
Terminal ballistics (wound ballistics)
What happens when the bullet hits the target
Components of typical “round”
5.56 round (from M16/M4)
Distal femur – 5.56/55gr
Sequence of events
Firing pin or striker hits primer Primer detonation Ignition/deflagration* of powder Increase pressure within casing d/t expanding gases Bullet forced from casing into rifling of barrel Rifling imparts “spin” as bullet traverses barrel length Bullet leaves barrel, followed by hot, stillexpanding gases (creates muzzle blast and muzzle flash) * deflagration – rapid burning (NOT explosion)
Primer indentation
Muzzle blast the sound associated with the round being fired
Muzzle flash the light or flame associated with the round being fired
http://www.filmfodder.com/
Physics of recoil For every action, there is an equal & opposite reaction Bullet travels forward, case is forced backwards against the breechface or breechblock, causing recoil In an automatic or semi auto matic weapon, this recoil is what drives the action to “cycle” http://www.firearmsid.com/A_featurevideo. htm
Forensic applications
Primer strike
Case head toolmarks
→
firing pin toolmarks
Breechface markings
Extractor markings
Ejector markings
Powder types
Sabot round
Speed of sound
In air:
344 m/s, or 1128 fps, or ~770 mph
In water:
1480 m/s or, 4856 fps. > 3000 mph
Super-sonic round
Sub-sonic round
Super-sonic – large caliber
“shot column” – shotgun pellets
Terminal ballistics
http://www.glenbrook.k12.il.us/
http://www.glenbrook.k12.il.us/
Useful terms….. PII – Point of Initial Intersect. This is where the bullet crosses the LOS (Line of Sight) for the first time. MO – Maximum Ordinate. This is the highest point the bullet reaches during its parabolic flight path. PSI – Point of Secondary Intersect. This is the point where the bullet crosses the LOS for the second time.
More terms…….
POI – Point of Impact. This is the point where the bullet impacts the target.
POA – Point of Aim. This is where the shooter was aiming the weapon.
If the sights are properly adjusted:
POI = POA (= DOA)
Mechanics of projectile wounding
Location
Penetration
Temporary wound cavity
Permanent wound cavity
Projectile deformation/fragmentation
Location
Penetration
Temporary wound cavity
Permanent wound cavity
Projectile deformation
Mechanic of projectile wounding
Physical cutting/crushing of tissue
Caliber related
Kinetically disrupting/stretching tissue that is adjacent to the path of the projectile
Low velocity (most handgun rounds) High velocity (rifle rounds & shrapnel from explosions) KE = ½ m x v2
