Ballistics Ballistics
Forensic Science IIForensic Science II
BallisticsBallistics
Machinegun BarbieMachinegun Barbie
meetsmeets
Benny “the chimp” GambinoBenny “the chimp” Gambino
BallisticsBallisticsthe study of projectiles, trajectories, and the effect on the targetthe study of projectiles, trajectories, and the effect on the target
Internal ballisticsInternal ballistics What happens in the weaponWhat happens in the weapon
External ballisticsExternal ballistics What happens after the bullet leaves the barrelWhat happens after the bullet leaves the barrel
Terminal ballistics (wound ballistics)Terminal ballistics (wound ballistics) What happens when the bullet hits the targetWhat happens when the bullet hits the target
Components of typical “round”Components of typical “round”
5.56 round (from M16/M4)5.56 round (from M16/M4)
Distal femur – 5.56/55grDistal femur – 5.56/55gr
Sequence of eventsSequence of events Firing pin or striker hits primerFiring pin or striker hits primer Primer detonationPrimer detonation Ignition/Ignition/deflagration*deflagration* of powder of powder Increase pressureIncrease pressure within casing d/t expanding within casing d/t expanding
gasesgases Bullet forced from casing into Bullet forced from casing into rifling of barrelrifling of barrel Rifling imparts “spin” as bullet traverses barrel Rifling imparts “spin” as bullet traverses barrel
lengthlength Bullet leaves barrel, followed byBullet leaves barrel, followed by hot, still- hot, still-
expanding gases expanding gases (creates(creates muzzle blast muzzle blast and and muzzle flashmuzzle flash))
* deflagration – rapid burning (NOT explosion)* deflagration – rapid burning (NOT explosion)
Primer indentationPrimer indentation
Muzzle blastMuzzle blastthe sound associated with the round being firedthe sound associated with the round being fired
Muzzle flashMuzzle flashthe light or flame associated with the round being firedthe light or flame associated with the round being fired
http://www.filmfodder.com/http://www.filmfodder.com/
Physics of recoilPhysics of recoil
For every action, there is an equal & For every action, there is an equal & opposite reactionopposite reaction
Bullet travels forward, case is forced Bullet travels forward, case is forced backwards against the breechface or backwards against the breechface or breechblock, causing recoilbreechblock, causing recoil
In an automatic or semi auto matic In an automatic or semi auto matic weapon, this recoil is what drives the weapon, this recoil is what drives the action to “cycle”action to “cycle”
http://www.firearmsid.com/http://www.firearmsid.com/A_featurevideo.htmA_featurevideo.htm
Forensic applicationsForensic applications
Primer strike Primer strike → → firing pin toolmarksfiring pin toolmarks Case head toolmarksCase head toolmarks
Breechface markingsBreechface markings Extractor markingsExtractor markings Ejector markingsEjector markings
Powder typesPowder types
Sabot roundSabot round
Speed of sound Speed of sound
In air:In air: 344 m/s, or 1128 fps, or ~770 mph 344 m/s, or 1128 fps, or ~770 mph
In water:In water: 1480 m/s or, 4856 fps. > 3000 mph1480 m/s or, 4856 fps. > 3000 mph
Super-sonic roundSuper-sonic round
Sub-sonic roundSub-sonic round
Super-sonic – large caliberSuper-sonic – large caliber
““shot column” – shotgun pelletsshot column” – shotgun pellets
Terminal ballisticsTerminal ballistics
http://www.glenbrook.k12.il.us/
http://www.glenbrook.k12.il.us/
Useful terms…..Useful terms…..
PII – Point of Initial Intersect. This is PII – Point of Initial Intersect. This is where the bullet crosses the LOS (Line of where the bullet crosses the LOS (Line of Sight) for the first time.Sight) for the first time.
MO – Maximum Ordinate. This is the MO – Maximum Ordinate. This is the highest point the bullet reaches during its highest point the bullet reaches during its parabolic flight path.parabolic flight path.
PSI – Point of Secondary Intersect. This PSI – Point of Secondary Intersect. This is the point where the bullet crosses the is the point where the bullet crosses the LOS for the second time.LOS for the second time.
More terms…….More terms…….
POI – Point of Impact. This is the point where POI – Point of Impact. This is the point where the bullet impacts the target.the bullet impacts the target.
POA – Point of Aim. This is where the shooter POA – Point of Aim. This is where the shooter was aiming the weapon.was aiming the weapon.
If the sights are properly adjusted:If the sights are properly adjusted:
POI = POA (= DOA)POI = POA (= DOA)
Mechanics of projectile woundingMechanics of projectile wounding
LocationLocation PenetrationPenetration Temporary wound cavityTemporary wound cavity Permanent wound cavityPermanent wound cavity Projectile deformation/fragmentationProjectile deformation/fragmentation
LocationLocationPenetrationPenetration Temporary wound cavityTemporary wound cavity
Permanent wound cavityPermanent wound cavity Projectile deformationProjectile deformation
Mechanic of projectile woundingMechanic of projectile wounding
Physical cutting/crushing of tissuePhysical cutting/crushing of tissue Caliber relatedCaliber related
Kinetically disrupting/stretching tissue that Kinetically disrupting/stretching tissue that is adjacent to the path of the projectileis adjacent to the path of the projectile Low velocity (most handgun rounds)Low velocity (most handgun rounds) High velocity (rifle rounds & shrapnel from High velocity (rifle rounds & shrapnel from
explosions)explosions) KE = ½ m x vKE = ½ m x v22
Permanent & temporary Permanent & temporary wound cavitieswound cavities
Cannelure fragmentation Cannelure fragmentation
Fragmentation effectFragmentation effect
Bullet deformationBullet deformation
GSR patternGSR pattern
GSR patternGSR pattern
stipplingstippling
Searing of clothing & skinSearing of clothing & skin
Entrance wound searingEntrance wound searing
Soot on clothingSoot on clothing
Muzzle imprintMuzzle imprint
Shored contact woundShored contact wound
Shotgun – close rangeShotgun – close range
Striae formation - shotgunStriae formation - shotgun
Pellet dispersionPellet dispersion
http://www.rit.edu/~andpph/exhibit-shotgun-blast.html
http://www.rit.edu/~andpph/exhibit-shotgun-blast.html
http://www.rit.edu/~andpph/exhibit-shotgun-blast.html
http://www.rit.edu/~andpph/exhibit-shotgun-blast.html
http://www.cuttingedgetraining.org/
http://www.pulsephotonics.com/gallery.htm
Pellet dispersionPellet dispersion
Shotgun – intermediate distanceShotgun – intermediate distance
HV GSW – exit wound frontal boneHV GSW – exit wound frontal bone
Glaser “safety slug” exit woundGlaser “safety slug” exit wound
.50 BMG at nearly 1 mile!!!!!!.50 BMG at nearly 1 mile!!!!!!