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!!!!!!