Weaponology and Traumatology of Firearms

Christopher I'Anson 1

ML Services and Training Ltd

Weaponology and Traumatology of FirearmsBy Christopher I’Anson

Director at ML services and training Ltd



CONTENTS

Physics of trauma Causes of death in gunshot wounds

(GSWs) Weaponology

Rifles Handguns Bullet design Shotguns



Physics of trauma



Physics of trauma There are several different types of energy:

Kinetic Thermal Gravitational Potential Energy Chemical Elastic Magnetic Light Sound Electrical (Nuclear)



Physics of trauma

Each for is important Energy can not be created or

destroyed Therefore it dissipates into other forms▪ This is what causes injury▪ Bullets transfer kinetic energy into different

forms which cause damage



Physics of trauma

This is the energy exchange that occurs when a bullet is fire from a weapon

Chemcial(Gunpowder)

Kinetic(as bullet is propelled outwards)

BULLET HITS TARGET•Thermal•Kinetic•Sound



Physics of trauma: Kinetic energy Kinetic energy is the most common form

of energy found in trauma.

If we look at the example of the bullet again, half the mass of the bullet times its speed is equal to the amount of kinetic energy it has and there for the amount of damage it will inflict.

Kinetic Energy= ½ mass x velocity



Physics of trauma: Kinetic energy Hence a small slower speed projectile like a

shotgun pellet does not do as much damage on a target as a larger 50 calibre bullet from a high powered rifle.

This must be considered when treating a patient who has been hit by such projectiles.



Projectiles

Projectiles are difficult to predict in terms for the damage they cause for a number of reasons: the power of the weapon item producing the projectiles is not always

known they may do any of the following: CAVITATION

FRAGMENTATION

RICOCHET



Projectiles: Cavitation Cavitation is where the projectile forms a cavity

or hole after penetrating tissue. There are two types of cavity formed, TEMPORARY and PERMINANT.

A temporary cavity, as the name suggests, is a cavity the is formed by a projectile as it passes through an object but does not remain after that object has passed.

The permanent cavity is the cavity that remains after the projectile is no longer acting on the body. ▪ The greater the velocity and mass of bullet the greater the cavity

size▪ 7.62 rifle > hand gun



Projectiles: Cavitation

The picture on the left is a diagram of cavity formation. Here you can see the temporary cavities marked by blue arrows, the black indicates the direction of the bullet, the red arrows show the permanent cavities. The picture the right is a picture of some ballistic gel as a bullet passes through it. The best (and most interest) way to view this is by looking at examples on YouTube.



Projectiles: Cavitation/ Wounding factors The size of the permanent cavity and

the wounding depends on: Bullet size Bullet weight Bullet design Bullet Speed Tissue damaged Depth of penetration



Projectiles: Fragmentation Fragmentation is where the projectile disintegrates

resulting in more than one piece of projectile acting on the body.

These can result in unpredictable damage to the body and the fragments may continue to have velocity and travel through tissue after fragmentation has occurred.

Fragments of bone can also cause fragmentation injury and act as secondary projectiles.

5.56mm bullets (e.g. SA8O) cause most of their damage by fragmentation.



Projectiles: Ricochet

Ricochet is where the projectile deflects and alters its path this again means that the path and

damage is not easily predicted ▪ however the presence of an exit wound may

help detect if this has occurred and the potential damage that may have occurred.▪ NB: just because there are two holes

does not mean that there is an entry and exit



Questioning the patient

You should ask: What weapon was used Type of shot (bird, hollow-points etc.) Number of gunshots herd Proximity of shot



Entry and Exit wounds Every victim of a gunshot wound has an entry

wound The size of this depends on the weapon used They may have an exit wound but not necessarily The presence of two wounds does not always mean one

is an exit wound and the other an entry

The presence of an exit wound depends on a number of factors

The exit will always be larger than the entry wound



Entry and Exit wounds: Exit wounds The location/ presence of an exit wound

will depend on: Ricochet inside the body Type of round▪ Hollow-points and half jackets are less likely to have

one▪ Shot guns using bird shot at a standard range are

unlikely to have exit wounds Velocity of round Position of the patient



Entry and Exit wounds: Exit wounds

A

If patient B was hit by a rifle bullet then you would expect the bullet to enter the front of the chest and exit near the shoulder blade

If patient A was hit in the same part of his chest as B it would exit lower down as he is bent over

B



Cause of death (COD) in GSW Tissue destruction

Less come COD▪ The body only needs a small about of tissue to survive i.e.

the brain stem

Bleeding (most common COD) Decreased blood pressure Loss of consciousness Vomiting Airway compromise Capillary pressure is less than intra-cranial pressure

causing cerebral vessels to collapse



Weaponology

By Christopher I’Anson



Rifles

Rifles come in different sizes with different calibre rounds (diameter of round) Range from 50 cal to 5.56 cal

The larger the calibre the heavier to bullet

The heavier the bullet the more energy is transferred into the target

The more energy transfer the more damage



Rifles

Rifles are the most powerful type of gun at medium-long range and therefore most deadly (shotguns at close range are more deadly)



Rifles

Table 1: This table shows the details of different weapons and their bullet

Rifle name Calibre (mm) Weight of bullet (grains)

Speed of bullet (m/sec)

AK 47 7.62 126-176 850SLR 7.62 -------- --------SA8O 5.56 55-62 900AK74 5.45 -------- --------



Rifles

The AK47 and SLR have a large calibre round and cause the most damage They have a large permanent cavity Their bullets tumble as they loss velocity



Rifles: SA8O

The round from the standard British armed forces rifle is the fastest in the table

It does its damage by fragmentation This maximises the size of the permanent

cavity Fragmentation occurs after the bullet hits the

target It may occur after the bullet exits the target



Handguns

Handguns account for 70% of GSWs in the USA

They are 1/10th as powerful as rifles They have two mechanism of injury

(MOI):1. Crush mechanism (permanent

cavity): this is the hole the bullet makes as it passes through tissue

2. Stretch mechanism (temporary cavity)



Handguns

The MOI are similar to that of a rifle However there is very little stretch

damage and a small temporary cavity unlike a rifle

Therefore most of the damage is done via the crush mechanism▪ This makes handguns less effective at

stopping people▪ Victims can continue attacking or run away

after


28

Handguns

Handguns have a lower velocity They are less likely to have an exit

wound There damage/ stopping power comes

from direct injury to vital organs such as the brain, heart or liver

Christopher I'Anson



Handguns

Here you can see the comparison between the cavities a rifle makes (A) and that of a pistol (B) NB: the rifle bullet has

also fragmented unlike the pistol

A

B



Bullet design

Bullet designs for rifles and handguns vary Full metal jacket: fully encased in metal

with lead Half jackets: exposed lead tip to allow

the bullet mushroom out on impact (bottom right)

Hollow-points (bottom left): similar to half jackets



Shotgun

Shotguns use cartridges that contain multiple pieces of shot. Can be up to 200 small balls (bird shot)▪ Can be glued to getter to make a slug which

is deadly Larger shards (buck shot)▪ For large animals



Shotgun

This is an x-ray of a patient who way shot with birdshot You can see multiple

small pellets The spread shows the

shot was at medium range

The shots are only superficial with minimal damage



SUMMARY

Energy always transfers into other forms This causes damage

Many types of weapon and shot Varies the type and severity of injury

Bullet trauma is multi-factorial

Documents

Weaponology and Traumatology of Firearms