Weaponology and Traumatology of Firearms

1. By Christopher I’Anson Director at ML services and training Ltd Weaponology and Traumatology of Firearms Christopher I'Anson

2. CONTENTS • Physics of trauma • Causes of death in gunshot wounds (GSWs) • Weaponology • Rifles • Handguns • Bullet design • Shotguns Christopher I'Anson

3. Physics of trauma Christopher I'Anson

4. Physics of trauma • There are several different types of energy: • Kinetic • Thermal • Gravitational Potential Energy • Chemical • Elastic • Magnetic • Light • Sound • Electrical • (Nuclear) Christopher I'Anson

5. 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 Christopher I'Anson

6. Physics of trauma This is the energy exchange that occurs when a bullet is fire from a weapon Christopher I'Anson

7. Physics of trauma: Kinetic energy Kinetic Energy= ½ mass x velocity 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. Christopher I'Anson

8. 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. Christopher I'Anson

9. Projectiles CAVITATION FRAGMENTATION RICOCHET • 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: Christopher I'Anson

10. Projectiles: Cavitation • Cavitationis 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 Christopher I'Anson

11. Projectiles: Cavitation The picture on the left is a diagram of cavity formation. Here you can see the temporary cavities marked by bluearrows, the black indicates the direction of the bullet, the redarrowsshow 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. Christopher I'Anson

12. 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 Christopher I'Anson

13. 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. Christopher I'Anson

14. 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 Christopher I'Anson

15. Questioning the patient • You should ask: • What weapon was used • Type of shot (bird, hollow-points etc.) • Number of gunshots herd • Proximity of shot Christopher I'Anson

16. 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 Christopher I'Anson

17. 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 Christopher I'Anson

18. Entry and Exit wounds: Exit wounds A B 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 Christopher I'Anson

19. 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 Christopher I'Anson

20. By Christopher I’Anson Weaponology Christopher I'Anson

21. 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 Christopher I'Anson

22. Rifles Rifles are the most powerful type of gun at medium-long range and therefore most deadly (shotguns at close range are more deadly) Christopher I'Anson

23. Rifles Table 1: This table shows the details of different weapons and their bullet Christopher I'Anson

24. 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 Christopher I'Anson

25. 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 Christopher I'Anson

26. 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): • Crush mechanism (permanent cavity): this is the hole the bullet makes as it passes through tissue • Stretch mechanism (temporary cavity) Christopher I'Anson

27. 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 Christopher I'Anson

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

29. Handguns A B • 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 Christopher I'Anson

30. 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 Christopher I'Anson

31. 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 Christopher I'Anson

32. 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 Christopher I'Anson

33. 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 Christopher I'Anson