CRIMINAL
INVESTIGATIONS
AMMUNITION/
BALLISTICS
AMMUNITION

Cartridge Structure
– Cartridge Case
– Primer
– Head
– Propellant
– Bullet
– Blanks- No Bullet
Metal Jacket
Ammunition
AMMUNITION

Cartridge Cases
– Made of Brass
• 30% Copper
• 30% Zinc
– Aluminum
– Brass, Plastic and Paper for shotguns
AMMUNITION

Function of Cartridge
– Expand and seal chamber
– Increase Gas Pressure
– Press the case up against barrel
– Seals
– Springs back to almost same size
– Aids extraction
AMMUNITION

Shapes
– Straight
– Bottle neck
• Permits more powder
– Tapered
• Not in use
Ammunition
AMMUNITION

Case Head Designs
– Rimmed
– Semi-rimmed
– Rimless
– Rebated
– Belted
Rimmed

Rimmed cartridges
use the rim to hold
the cartridge in the
chamber of the
firearm, with the rim
serving to hold the
cartridge at the
proper depth in the
chamber this
function is called
“headspacing”
Semi-Rimmed

On a semi-rimmed
case the rim
projects slightly
beyond the base of
the case, though not
as much as a
rimmed cartridge.
Rimless

On a rimless case,
the rim is the same
diameter as the
base of the case
 It is known as an
extractor groove.
Since there is no rim
projecting past the
edge of the case
Rebated


Rebated rim cartridges
have a rim that is
significantly smaller in
diameter than the base of
the case, serving only for
extraction.
Functionally the same as
a rimless case, the
rebated rim provides some
additional benefits when
considered in conjunction
with other cartridges.
Belted

The purpose of the
"belt" on belted
cases is to provide
headspacing.
 The extractor
groove is cut into
the belt just as it is
cut into the case
head on a rimless
case.
 The belt as as a rim
on what is
essentially a rimless
case
AMMUNITION

Caliber Nomenclature
– Rifled barrels
• Lands and grooves
– Diameter of bore from land to land
– Sometimes groove to groove diameter
– Bullet diameter
AMMUNITION

Types of Cartridge
– R = Rimmed
– SR = Semi-Rimmed
– RB = Rebated
– B = Belted
– No letter for rimless
AMMUNITION

Additional Terms
– Magnum = Higher velocity than standard
– Wildcat = Nonstandard, produced by small
entity
AMMUNITION

Head Stamps (Cont.)
– Civilian made with manufacturers symbol
– Military made with initials or codes
•
•
•
•
Year of manufacturing
Match/nm = military match grade ammo
+ = NATO
+P or +P+ = High Pressure
AMMUNITION

Caliber Specification
– U.S. System not consistent or accurate
– .303 Savage = .308 bullet
– .303 British = .312 bullet
– .30-06 and .308 both fire a .308 bullet
– .06 refers to year made
AMMUNITION

U.S. Caliber Designation
– Confusing
– Not accurate
– .38 and .357
– Difference is length of case and grains of
powder
AMMUNITION

Black Powder Cartridges
– Designated by:
• Caliber
• Black powder charge
• Bullet weight
– Examples:
» 45-70-405
» Some smokeless powder cartridges used this
designation
» .30-30
AMMUNITION

Metric Designation
– Bullet diameter
– Case length
– Type of cartridge
AMMUNITION

Head Stamps
– All cases have stamps on bases
– Imprinted for Identification Purposes
•
•
•
•
Letters
Numbers
Symbols
Trade names
AMMUNITION

Bullet Powder Weights
– Grain = weight not granules
– 1 oz. = 437.5 grains
– 1 grain = .0648 grams
– Bullet and powder weights measured in
grains
AMMUNITION

Primer (Cont.)
– Non-corrosive/Non-mercuric
– Lead Styphnate
– Barium Nitrate
– Antimony Sulfide
– Most U.S. primers contain all three
• *Detection of these compounds provides bases
for GSR
AMMUNITION

Primers (Cont.)
– Rimfire Ammo
• No primer assembly
• Primer chemical is in rim
AMMUNITION

Propellants
– Black Powder
• Charcoal
• Sulfur
• Potassium Nitrate
– Charcoal is fuel
– Nitrate supplies oxygen
– Sulfur creates density
AMMUNITION

Propellants – Black Powder
– When powder burns
• Gas = 44%
• Residue= 56%
– Residue appears as dense white smoke
AMMUNITION

Smokeless Powder
– 1884 Vieille – French Chemist
– Nitrocellulose
– Used EtOH/Ether
– Rolled into sheets
– Cut into flakes
– Single base
AMMUNITION

Smokeless Powder (Cont.)
– 1887 – Alfred Noble
– Nitrocellulose and Nitroglycerine
– Rolled and cut into flakes
– Double base
AMMUNITION

Ball Powder Winchester
–
–
–
–
–
–
–
1933
Nitrocellulose dissolved
Formed into balls
Different diameters
Appears uniform round, black spheres or ovals
Reflective surface
Flattened round
• Irregular
• Flattened chips
– Wide variation between round and flat
AMMUNITION

Powder Grains
– Disk
– Flake
– Cylinder
– Uncoated (Greenish color)
– Coated w/Graphite (shiny black)
Rod Gun Powder
Ammunition

Powder (continued)
– Powders burn at different rates
– Gases and unburned grains are
discharged upon firing
– Grains can be found in clothing and skin
Ammunition
Bullet
– Originally lead spheres
– Musket vs.. Rifle
– Minnie ball (Capt.. Minnie, French Army)
– Modern bullets
• Lead
• Metal-jacketed
Ammunition

Bullets
– Various shapes
•
•
•
•
Round
Hollow point
Semi-wadcutter
Wadcutter
Ammo performance-Handguns
Cartridge
.380
9mm
.40 S&W
.45 ACP
.38
.357
.44 mag
Bullet gr.
95
124
155
230
158
158
240
Velocity
955
1299
1140
855
755
1235
1350
Ft-lbs
190
465
447
405
200
535
971
Ammo performance-Rifles
Cartridge
Bullet gr.
Velocity
Ft-lbs
.223
55
3150
1218
5.45x39
53
2985
1053
.270
130
3060
2702
.30-30
150
2390
1902
.308
150
2750
2520
.30-06
150
2740
2500
Bullet Comparison

Class characteristics
– Number of lands and grooves
– Diameter of lands and grooves
– Width of lands and grooves
– Depth of lands and grooves
– Direction of rifling twist
– Degree of twist
Bullet Comparison

Individual Characteristics
– Imperfections on lands/grooves
– Score the bullets
– Jacketed bullets, more pronounced
– Are peculiar to each firearm
Bullet Comparison

Factors impacting Ind. Characteristics
– Rusted barrel
– Jacketed/unjacketed
– Velocity/pressure
– Bullets vary from lot to lot
Bullet Comparison

Additional markings
– Skid marks
– Shaving

Compositional Analysis
– Fragments are recovered
– SEM-EDX
– Comparison between suspected guns
bullets and recovered fragments
Bullet Comparison

Base markings
– Imprinted from propelled powder grains
– Most evident in bullets w/lead base
– Shorter barrel, deeper marks
– Different forms produce different marks
• Spherical=circular pits
• Disk=circular imprints
• Black powder=peppered
Bullet Comparison

Additional factors
– Bullets fired in wrong caliber weapon
– Decomposed bodies (Study after 66 days)
• Nylon clad-unaffected
• Aluminum-mildly affected
• Lead bullets, recovered from
– Brain, chest cavity, abdomen-mild tarnish
– Fat, muscle-severe oxidation-impaired match
• Copper alloy-severe degradation
Bullet Comparison

Surface analysis of bullet
– Non-organic material
– Tissue analysis

DNA typing
Cartridge Case Comparison

Comparison “MAY” make ID possible
– Type
– Make
– Model

Test and evidence cartridges compared
– Use same brand and lot

Ammo consistency
Cartridge Case Comparison

Markings=imprints or scratches
– Magazine marks
– Breech block marks
– Firing pin marks
– Size,shape, and location of;
• Extractor and ejector marks
– Flute marks
Physics of
Penetrating Trauma

Recall Kinetic Energy Equation
Mass ( weight )  Velocity ( speed )
KE 
2
2
– Greater the mass the greater the energy
• Double mass = double KE
– Greater the speed the greater the energy
• Double speed = 4x increase KE
(continued)
Physics of
Penetrating Trauma

Small & Fast bullet can cause greater damage
than large and slow.
– Different bullets of different weights
traveling at different speeds cause
• Low Energy/Low Velocity
– Knives and arrows
• Medium Energy/Medium Velocity Weapons
– Handguns, shotguns, low-powered rifles
– 250-400 mps
• High Energy/High Velocity
– Assault Rifles
– 600-1,000 mps
(continued)
Physics of
Penetrating Trauma

Bullet spins as it travels down barrel
– Rifling in barrel
– Allows bullet to travel straight with slight
yaw

Bullet departs barrel, spinning with a slight
wobble or yaw

Weapon forced backward and absorbs
energy
– Recoil
(continued)
Physics of
Penetrating Trauma

Remainder of energy propels bullet forward
at a high rate of speed.

Trajectory is curved due to gravity

As bullet strikes object, it slows and energy
is transferred to object.
– Law of Conservation of Energy
Energy Dissipation

Drag:
– wind resistance

Cavitation:
– formation of a partial vacuum and cavity within a semi-fluid medium

Profile:
– Size and shape of a projectile as it contacts a target
– Larger the profile=greater energy exchange
– Expansion and fragmentation results in damage

Stability
– Allows for straighter trajectory
– Decreases after striking object results in tumbling
Aspects of Ballistics

Velocity
– Causes Trajectory
• Faster = straighter trajectory
• Slower = more curved due to gravity
Aspects of Ballistics

Profile
– Portion of bullet you see as it travels
towards you
• Larger profile = greater energy exchange
– Caliber
• Diameter of a bullet (ID of gun)
– 0.22 caliber = 0.22 inches
– Bullets become unstable as they pass from
one medium to another.
Aspects of Ballistics

Expansion & Fragmentation
– Results in increased profile
– Mushrooming
– Initial impact forces may result in
fragmenting
– Greater tissue damage
Aspects of Ballistics

Secondary Impacts
– Bullet striking other objects can cause yaw
and tumble
– Body Armor (Kevlar)
• Transmits energy throughout entire vest
resulting in blunt trauma
– Myocardial Contusion
– Pulmonary Contusion
– Rib Fractures

Shape
– Handgun Ammunition = Blunt = Tumble
– Rifle Ammunition = Pointed = Piercing
Specific Weapon Characteristics

Handguns
– Small caliber, short barrel, medium-velocity
– Effective at close range
– Severity of injury based upon organs damaged

Rifle
– High-velocity, longer barrel, large caliber
– Increased accuracy at far distances

Assault Rifles
– Large magazine, semi- or full-automatic
– Similar injury to hunting rifles
– Multiple wounds
Ballistics

Ballistics=Study of motion of projectiles
– Internal
– External
– Terminal
• Wound ballistics
Specific Weapon Characteristics

Shotgun
– Slug or pellets at medium velocity
• 00 (1/3”) to #9 (pin head sized)
• Larger the load, the smaller the number of
projectiles
• Deadly at close range
Damage Pathway

Projectile Injury Process
– Tip impacts tissue
– Tissue pushed forward and to the side
– Tissue collides with adjacent tissue
• Shock wave of pressure forward and lateral
– Moves perpendicular to bullet path
– Rapid compression, crushes and tears
tissue
– Cavity forms behind bullet pulling in debris
with suction.
Damage Pathway

Direct Injury
– Damage done as the projectile strikes tissue

Pressure Shock Wave
– Human tissue is semi-fluid
– Solid and dense organs are damaged greatly

Temporary Cavity
– Due to cavitation

Permanent Cavity
– Due to seriously damaged tissue

Zone of Injury
– Area that extends beyond the area of permanent injury
Ballistics Cavitation
Specific Tissue &
Organ Injuries

Density of tissue affects the efficiency of
energy transmission
– Resiliency
• Strength and elasticity of an object

Connective Tissue
– Absorbs energy and limits tissue damage

Organs
– Solid Organs
• Dense and low resilience
– Hollow Organs
• Fluid filled: transmit energy = increased damage
• Air filled: absorbs energy = less damage
Specific Tissue &
Organ Injuries

Lungs
– Air in lung absorbs energy
– Parenchyma is compressed and rebounds
– Pneumothorax or hemothorax can result

Bone
– Resists displacement until it shatters
– Alters projectile path
General Body Regions

Extremities
– Injury limited to resiliency of tissue
– 60-80% of injuries with <10% mortality

Abdomen (Includes Pelvis)
– Highly susceptible to injury and hemorrhage
– Bowel perforation: 12-24 hrs peritoneal irritation

Thorax
– Rib impact results in explosive energy
– Heart & great vessels have extensive damage due to lack of
fluid compression
– Any large chest wound compromises breathing
Ballistics
Ballistics

Temporary/Permanent Cavity
– Max diameter of temp cavity is proportional to
amount of kinetic energy lost
– Occurs at maximum yaw or fragments
– Yaw continues until Cg is forward or approx 180
degrees rotation
– Size of cavity is determined by amount of K.E. lost
by bullet
– Size of cavity is determined to a degree by cross
section of round
Ballistics

Temporary/Permanent Cavity (cont.)
– Compression, stretching, tearing of tissue
– Handguns-Damage to area hit by bullet,
very little collateral damage
– Rifles-Radial damage to nerves, tissue,
vessels, organs not struck by bullet
– Damage related to density, elasticity and
cohesiveness of tissue
– Muscle vs. Liver vs. Lung
General Body Regions

Neck
– Damages Trachea and Blood Vessels
– Neurological problems
– Sucking neck wound

Head
– Cavitational energy trapped inside skull
– Serious bleeding and lethal
Ballistics
Ballistics

Energy loss along wound track
– Not uniform
– Changes and variations occur due to;
• Angle of yaw
• Change in density of tissue
• Change in structural dimension of bullet (mushrooms)
– Fragmentation amplifies effect
• .223 marked yaw at 12cm
• Major frag/tissue disruption at 15-25cm
Ballistics
Ballistics

Critical velocity
–
–
–
–
–
–
–
At or above 2625-2953 ft/sec (FMJ)
At or above 1500-2000 ft/sec (expanding ammo)
Tissue damage more severe
Supersonic flow = strong shockwaves
Shockwaves travel through body
Damage is 20-30 times larger
Due to higher amount of K.E. loss
Ballistics

Critical amount of K.E. loss
– Wounds are more severe
– Exceeds elastic limits
– Organ bursts
– Projectile does not have to be near organ
Ballistics

Critical amount of K.E. loss-Head
– Special case
– Cranial cavity is a closed, rigid structure
– 1% elasticity
– No place for energy to disperse
– Results in bursting injuries (high velocity)
Ballistics

Temporary cavity structure
– FMJ
– Hunting rifle round
– Shotgun pellet
Ballistics

Temporary cavity size
– 10-12 times diameter of bullet
– High K.E. loss-20-30 times bullet

Permanent Cavity size
• Handgun=smaller than round diameter
• High velocity=size of bullet
• Unless Elastic limit of tissue is reached=large
irregular tearing wound track.
Case Study

This case involved a barroom
shooting. The incident went
something like this:
Case Study

Guy No.1- "Hey man, my quarters
were up next!! I've got the next
game on that pool table!!"
Case Study

Guy No. 2- "Man you’re
crazy! I've had my quarters up
there for over an hour!"
Case Study

Guy No. 1- "Oh yeah? Well not
only are my quarters up next but
your breath stinks too!!!"
Case Study

Guy No. 2- "You son-of-aXXXXX!!!!! I'm gunna kill you!!!"
Case Study

Me- "Now guys, calm down it's
only a pool game; it's only a
quarter."
Case Study

Guy No.1 pulls out the Llama 45
auto below and points it at Guy
No. 2.
Case Study

In a drunken stupor he fires a
single shot at Guy No. 2, missing
him and hitting me right between
the eye's with this 45 AUTO, 230
grain full-metal-jacketed bullet.
Case Study

At the same time the pistol ejects
the 45 AUTO cartridge case below
into the corner pocket of the pool
table.
Case Study

Guy No. 1 and Guy No. 2 run out
of the bar get in a car and go
home. They tell mom they have
been to the movies, hide the gun
under their bunk bed and go to
sleep.
Case Study

Meanwhile back at the bar, a riot
has ensued because the other
guys with quarters on the table are
really p------ off because the spent
case has jammed the pool
table. Order is finally restored
when county police detectives
clear the table.
Case Study

My cold lifeless body is taken to
the Medical Examiners Office for
the 9 AM autopsy.
Case Study

Guy's No. 1 and 2 are later roused
from bed by Detectives and the
pistol, it's magazine, and four 45
AUTO cartridges are recovered
from under the bed.
Case Study

The pistol, magazine, live
ammunition, spent case, and bullet
are later submitted to the lab for
analysis.
Case Study

Although my ex-coworker is all but
overcome with grief, he manages
to set aside his personal ties to the
case and conducts the required
analysis in a totally professional
and unbiased fashion.
Case Study

First course of business is to
examine the pistol, which is found
to be in perfect working
condition. The pistol is test fired in
the water tank and standards from
the pistol are compared to the
spent case from the pool table and
bullet from my head.
Case Study

The results of which are the match
seen below.
Case Study

Breech Marks: Standard from
pistol (left) compared
to the spent case from the bar
(right).
Case Study

Bullet land impression comparison:
Standard (left)
compared to "my" bullet (right).
Case Study

By the way, Guy 1 "walks" when
his brother testifies that I started
the fight by stealing his brother's
hot wings.
Case Study

They really do have the best hot
wings in town!!!
5.56 Centerfire vs. Rimfire
Some terminology
Barrel: the metal tube through which the
bullet is fired.
 Bore: the inside of the barrel, either:
Smooth bore: Shotguns.

Not smooth bore: rifles, pistols.

Muzzle: the end of the barrel out of
which the bullet comes out.

Primer: volatile substance that ignites
when struck to detonate the powder in
a cartridge.
Types of firearm weapons
Non-rifled: only long
 Rifled: short and long

What happens?
The holder presses the firing pin which in
turn strikes the primer which ignites the
powder and produces large amount of
hot gas.
Produces very high pressure that fires the
bullet forcefully through the barrel
leaving the muzzle, and onto the target.
Mechanism of injury:
As the missile traverses the body it causes injury
by:
1. Basic contact of bullet and it’s fragments with the
tissue, so larger bullets create bigger damage at
the same velocity.
2. Transferring some of its available kinetic energy to
the tissue around it, so increasing velocity greatly
increases damage.
3. It also causes cavitations in the tissue it passes as it
accelerates molecules → makes them move
centrifugally away from the axis of the bullet.
 Bullets do not typically follow a straight line to the
target. Rotational forces are in effect that keep the
bullet off a straight axis of flight.

SO…
Mode of injury depends on the velocity of
the missile
-Slow velocity (<340 m/s) speed of sound in
air or less
-High velocity (1500 m/s) faster!
 High velocity missile causes a shockwave
around it’s track → severe disruption →
↑tissue pressure and more damage.
 So a 10mm wide bullet may cause a 15mm
wide track of damage…

Smooth bore weapon
(Shotgun):
A
gun with a smoothbore that shoots cartridges
that contain "shot" or small metal pellets (of lead
or steel) as the projectiles.
 Ammunition: A shotgun shell(cartridge) may
contain one large projectile (called a slug), a
few pellets of large shot, or many tiny pellets.
Cartridge made of a cylinder fitted into a metal
base contains charge of propellant, wads, and
shots.
 Range is the most important factor, and can be
estimated in over half of cases… Close range
wounds are severe, but at even relatively short
distances, wounding may be minimal.
The rifle weapon:




Rifles differ from shotguns in the length of
the barrel and the presence of a butt stock.
They fire one projectile at a time through a
thicker barrel that has spiral grooves on its
inner surface → rotational movement.
They are much more accurate and shoot
more powerful cartridges than handguns.
Ammunition: metal cylinder loaded with
explosive propellant and bullet.
Rifle bullet/pistol
bullet
Ballistics

Forces
– K.E.=1/2mv2
– Velocity place larger role in force
– Doubling mass, doubles force
– Doubling velocity quadruples force
– Energy transfer/loss
Ballistics

Energy Loss/transfer
– Amount of K.E. upon impact
– Angle of yaw upon impact
– Caliber, construction, shape
– Density, strength, elasticity of tissue
Ballistics-Structural Mechanics
Elasticity (Stretching)
 Shearing
 Compression
 Cohesiveness
 Tensile strength
 Density

Ballistics
Movement through body
–
–
–
–
–
–
Crushes/shred tissue in path
Flinging, radially, surrounding tissue
Temp. cavity several times (12) size of bullet
Lasts 5-10 msec
Pulsates, contractions and collapse
+/- pressure sucks in bacteria/foreign materials