7 Firearms and Ballistics

Rachel Bolton-King1* and Johan Schulze2* 1Department of Forensic and Crime Science, Staffordshire University, Stoke-on-Trent, Staffordshire, UK; 2Veterinary Forensic and Wildlife Services, Germany and Norway

7.1 Crime Scene Evidence: Firearms and Ballistics by Rachel Bolton-King 82 7.1.1 Introduction 82 7.1.2 Firearms 82 7.1.2.1 Types of frearm 83 7.1.2.2 Modern fring mechanisms 84 7.1.3 Ammunition 85 7.1.3.1 Composition 85 7.1.3.2 Live cartridges 86 7.1.3.3 Fired cartridge cases and projectiles 86 7.1.4 Internal ballistics 87 7.1.4.1 Primer 87 7.1.4.2 Propellant 87 7.1.4.3 Projectile 88 7.1.4.4 Weapon 88 7.1.4.5 Production of gunshot residue (GSR) 89 7.1.5 Intermediate ballistics 89 7.1.5.1 Propellant particles and gaseous combustion products 89 7.1.5.2 Projectile 90 7.1.5.3 Muzzle attachments 90 7.1.6 External ballistics 91 7.1.6.1 Muzzle velocity and kinetic energy 91 7.1.6.2 Trajectory 92 7.1.6.3 Range 94 7.1.6.4 Accuracy and precision 94 7.1.7 Terminal ballistics 95 7.1.7 Retrieval of fred ammunition components 95 7.1.8.1 Cartridges and fred cartridge cases 95

*Corresponding authors: [email protected]; [email protected]

7.1.8.2 Fired projectiles and shotgun wadding 96 7.1.8.3 Gunshot residue (GSR) 96 7.1.9 Conclusion 97 7.2 Wound Ballistics by Johan Schulze 99 7.2.1 Introduction 99 7.2.2 Basics of wound ballistics 99 7.2.3 Some specifcs of wound ballistics 102 7.2.3.1 Deformation/fragmentation 102 7.2.3.2 Entrance and exit wound 102 7.2.3.3 Shotgun 104 7.2.3.4 Airgun 105 7.2.4 Essential steps of investigating a shot animal 106 7.2.4.1 Before necropsy 106 7.2.4.2 The practical approach 107 7.2.4.3 Recovery of bullets 112 7.2.5 Conclusion 113

7.1 Crime Scene Evidence: Firearms ammunition and ballistics. The focus will and Ballistics be on the common types of frearm and asso- ciated ammunition that are utilized by civilians, which would ultimately be en- RACHEL BOLTON-KING countered in the majority of cases where veterinarians are involved in forensic investi- gations. For more in-depth reading into this 7.1.1 Introduction feld, recommended reading includes Farrar and Leeming (1983), Carlucci and Jacobson Crime scenes involving shooting-related in- (2008), Heard (2008), Haag and Haag (2011), cidents can contain a raft of forensic evi- Warlow (2011). dence that may be of beneft to the forensic veterinarian and criminal investigating team. The nature of the frearm (Section 7.1.2) and the ammunition (Section 7.1.3) utilized 7.1.2 Firearms in the shooting have a critical role to play in the resulting injury and trauma exhibited The legal defnition of a frearm differs slightly in the body. from the dictionary defnition. A frearm is The term ballistics is defned as the defned by The Firearms (Amendment) Act study of the motion of projectiles. Ballis- 1988 (UK Parliament, 1988) as ‘a lethal bar- tics is divided into three main categories: relled weapon of any description from which internal (Section 7.1.4), external (Section 7.1.6) any shot, bullet or other missile can be dis- and terminal (Section 7.1.7); however, there charged’; whereas the Oxford English Dic- is also a fourth category known as inter- tionary (Oxford University Press, 2014) sim- mediate ballistics (Section 7.1.5). Terminal ply identifes a frearm as different types of ballistics (Section 7.1.7) covers both inani- gun, i.e. ‘a rife, pistol or other portable gun’, mate objects and living organisms; however, thus ‘gun’ is defned as ‘a weapon incorpor- the study of projectiles through living organ- ating a metal tube from which bullets, shells, isms is classifed as a sub-category of terminal or other missiles are propelled by explosive ballistics referred to as wound ballistics (see force, typically making a characteristic loud, Section 7.2). sharp noise’. The mechanism of fring the The feld of frearms and ballistics is projectile (Section 7.1.2.2) is unspecifed; extensive. This chapter, therefore, aims to however, the legal defnition implies that provide an introductory explanation of the weapon must be capable of killing a the scientifc theory underpinning frearms, living target. The dictionary states that an Firearms and Ballistics 83

explosive force is required; however, the force may not have to be explosive in order to be lethal. The legislation around frearm ownership, transportation and use will vary Muzzle extensively depending on the region in Chamber which the crime occurred. Barrel

7.1.2.1 Types of ﬁrearm Tr igger The term handgun is commonly used to describe any frearm that is capable of being Frame fred from one hand (AFTE Training and Standardization Committee, 2007). This Magazine term includes two types of frearm: revolver (or revolving pistol) and pistol, although the sub-machine gun (SMG) may also be con- Fig. 7.1.1. Annotated image of a Sig Sauer P226 sidered in this category. Within the UK, air semi-automatic pistol ﬁeld stripped into its key weapons are currently the most common component parts listed from top of the image; slide frearms utilized in gun crime as these are (containing the ejection port), barrel (with integral typically legal and unlicensed, but this is chamber), recoil guide spring, frame and magazine closely followed by handguns (Berman, (housed inside the grip of the frame). 2012; Smith et al., 2012) due to their small size, making them easy to conceal from and typically utilizes cartridges measured other civilians and law enforcement. Air in gauge rather than calibre. Gauge equates weapons are typically used for recreational to the number of lead balls with the diameter use, such as target shooting, whereas hand- of the barrel bore, that collectively weigh guns are typically utilized for self-defence. 1 lb. The calibre is either the internal diam- The main difference between a pistol eter of the mouth of the cartridge case or the and a revolver is that a revolver has a cylinder maximum diameter of the projectile (units containing multiple chambers, each capable may be metric or imperial). For example, a of housing a single ammunition cartridge, 12-gauge shotgun has a barrel diameter of and the chamber is therefore separated from 0.729 in. and 12 lead balls of 0.729 in. weigh the barrel. A pistol has a single chamber that 1 lb. Shotguns are usually single- or double- houses only one ammunition cartridge and barrelled with the latter having either a this is integrated into the barrel. A sub- side-by-side or up-and-over barrel align- machine gun is a shorter-barrelled, light- ment. Shotgun barrels also may contain a weight machine gun, designed to fre pistol- choke at the muzzle end, which can be inte- sized cartridges in short or long bursts of gral to the barrel or be removable. The choke fre. Modern handgun barrels are typically aims to force the multiple shot together rifed with a spiral internal surface profle prior to exiting the barrel and there are vary- consisting of alternating spiral lands and ing degrees of choke available. To be made grooves to enhance the ballistic properties of more concealable, criminals are known to the projectile upon muzzle exit. Figure 7.1.1 cut down and shorten the barrel length, indicates the key components common to a which will ultimately reduce the velocity, wide range of frearms. energy and range of the projectile(s) and in- Rifes also have a single chamber to crease the spread of lead shot fred from the house one cartridge, but are identifed by ammunition due to excessively high pressure their longer-rifled barrel and are larger (Haag and Haag, 2011) and choke removal. in overall size than handguns. Rifes are Tasers and stun guns may also be con- designed to be fred by one individual, but sidered as a frearm in some countries, in- using two hands. cluding Great Britain. Tasers are designed to A shotgun is differentiated from hand- fre two barbs from a cartridge, which are guns and rifes due to the smooth-bore barrel connected to the weapon by wire reaching 84 R. Bolton-King and J. Schulze

up to 10.6 m. When the wired barbs make the legal limits for an air weapon to be classi- contact with or penetrate the upper layer of fed as a frearm are higher than 1 ft lb (Home the skin (epidermis) the electrical circuit is Offce, 2014). Criminal use of air weapons complete and current is passed through the was on the rise until 2003/2004 (Berman, target’s tissue to incapacitate. Tasers can be 2012), when legislation aimed to reduce this used in stun drive mode to cause pain, (Squires, 2014). However, injuries to animals whereby the cartridge is not used and con- caused by air weapons are still more com- tact is made directly between the skin and monly observed by veterinarians. To be legal the electrical device. and unlicensed, air pistols must generate pro- Other weapons that could be considered jectile muzzle energy less than 6 ft lbs (8.1 J) relevant within the context of veterinary fo- and less than 12 ft lbs (16.3 J) for air rifes rensics are bows and crossbows, humane (Home Offce, 2014). However, in Northern killers such as captive-bolt guns (Warlow, Ireland, air weapons fring projectiles with 2011), airsoft weapons and paintball guns. muzzle energy greater than 1 J must be held However, by the UK legal defnition these on a frearms certifcate (Northern Ireland are not frearms and therefore not considered Offce, 2005). within the scope of this chapter. The ammunition is loaded into the weapon either manually, or automatically from a magazine or belt of ammunition. Auto- 7.1.2.2 Modern ﬁring mechanisms matic loading (self-loading) uses the energy created from discharging a previous cart- Firing mechanisms involve the loading of ridge to reload the next live cartridge of am- the projectile/ammunition into the weapon munition into the chamber ready to be fred and the functioning of all the frearm’s in- again. Heard (2008) and Warlow (2011) ternal components required to propel the discuss the range of fring mechanisms that projectile out of the barrel. Design and func- enable self-loading of ammunition and tionality of specifc frearms is an extensive examples include recoil, blowback and bolt- topic, ultimately determined by the frearm action. Principally, there are two overarching manufacturer. Forensic veterinarians do not automatic fring mechanisms: semi-automatic need to know the in-depth details of all fr- and fully automatic. Semi-automatic means ing mechanisms, but need to appreciate that with one pull of the trigger, one cart- the differences in the key fring mechanisms ridge is fred. With fully automatic, one and how these infuence the ammunition pull of the trigger causes continual fring selected, the properties of the projectiles and reloading of ammunition until either the fred and the potential differences that trigger is released, or there is no ammunition could be expected for wound examination left to fre from the magazine or belt. There and interpretation. are some frearms designed to fre short Air weapons are relatively low-powered bursts of ammunition, whereby continual weapons, which use a high-pressure volume hold of the trigger will fre a small number of gas, typically atmospheric air or carbon of cartridges (usually three to fve); to fre dioxide, to transfer energy to the projectile further cartridges the trigger will need to (pellet) and propel it out of the barrel; these be released and pulled again. Modern weapons therefore do not require ignition of pistols such as Browning Hi-Power and Ber- chemical compounds to generate kinetic etta 92FS are commonly semi-automatic, energy. Air weapons using atmospheric air whereas SMGs such as MAC-10 and Uzi typically operate by manually compressing SMG may also have the capability of fully a spring; pulling the trigger releases the automatic fre and the AK47 assault rife spring compressing the air and pushing it may have the additional option of short- behind the pellet. Alternatively, the pellet is burst fre. fred utilizing a small jet of compressed gas, For handguns, there are two ways to set such as carbon dioxide, released from a the trigger and fre the weapon: single-action small gas canister attached to the weapon and double-action. Single-action requires a when the trigger is pulled. In most of the UK, manual cocking of the hammer and then a Firearms and Ballistics 85

subsequent pull of the trigger to fre. With designed frst for a specifc purpose; the weapon double-action, a longer and heavier pull of is developed later to fre that ammunition. For the trigger will frst cock the hammer and example, Georg Luger developed the 9 × 19 then release the fring pin/striker on to the mm cartridge in 1902 which was later designed cartridge causing it to discharge. to be fred in the 1908 Luger P08 semi-automatic For rifes and shotgun, the fring mech- pistol (Jones and Ness, 2009; Bolton-King, anisms include single-shot, bolt-action (bolt 2012). Thus, a wide range of ammunition with a is turned to lock the cartridge into the breech variety of specifcations has been developed end of the barrel before fring), self-loading for specifc purposes (Table 7.1.1); choosing the (similar to self-loading pistols) and pump- correct ammunition for a specifc weapon can action (breech is linked to the fore-end, which be critical to achieve the intended outcome. To when pulled back, unlocks the breech and ensure the weapon fres safely and correctly, ejects the cartridge case; pushing the fore-end the dimension(s) of the ammunition (calibre or forward loads in a live cartridge from the gauge) must be accurately selected for the fre- magazine and cocks the weapon). arm in which it is discharged. Other terms used to describe frearms and their fring mechanisms include converted 7.1.3.1 Composition (for example, a blank fring weapon converted to fre ammunition such as Olympic 38 or Modern ammunition has developed from Baikal), home-made, concealed (frearms made loading individual components (primer, propel- to look like other objects such as pen gun), de- lant and projectile) into a self-enclosed cart- activated (frearms made unable to fre am- ridge system to create a closed environment munition by machining/removing key compo- for a large amount of gas to be produced and nents), reactivated (deactivated weapons made allow the gas pressure to rise exponentially. to fre again) and imitation (frearms that look The core components of a cartridge are the real, but do not fre live ammunition). cartridge case and the projectile. The projectile is positioned at the mouth of the cartridge case and they are crimped together to form the cartridge. 7.1.3 Ammunition The base of the cartridge case houses the primer unit that contains the primer compound. Inside Like frearms, ammunition has developed the cartridge case, the propellant is confned over the centuries. However, ammunition is between the primer unit and the projectile.

Table 7.1.1. Common examples of modern ammunition calibres and their intended purpose.

Calibre (in.) Weapon Type (Centre-Fire) Purpose

0.22 Hornet Rifle Small varmint hunting (<200 m) 0.223 Remington Rifle Military standard (long range) 0.303 British Rifle Military standard (long range) 0.357 Magnum Revolver Law enforcement (short range) 0.410 Shotgun Small varmint/game hunting 0.45 Automatic Colt Pistol (ACP) Pistol Close combat, self-defence 0.458 Winchester Magnum Rifle Hunting dangerous game

Calibre (mm)

7.62 NATO Riﬂe Military standard (long range) 9 × 19 Pistol or sub-machine gun Military standard (short range)

Gauge

20 Shotgun Recommended for hunting novices 12 Shotgun Short range bird hunting 86 R. Bolton-King and J. Schulze

The primer (Section 7.1.4.1) and propel- fred from pistols, revolvers, rifes and ma- lant (Section 7.1.4.2) are both mixtures of chine guns are typically referred to as bullets. chemical compounds designed to ignite, burn Shotgun ammunition, however, commonly and provide oxygen to the combustion pro- contain multiple spherical lead pellets known cess. Priming compounds are typically inor- as shot. However, some shotgun cartridges are ganic compounds that are explosive and designed to fre a single projectile (slug) from more exothermic, whereas propellant fakes a rifed-barrel shotgun, commonly used for are organic in nature, burning slower and beast destruction. slightly cooler. There are two main classifcations of 7.1.3.2 Live cartridges modern cartridge: centre-fre and rim-fre. The difference is due to the location of the Although fred cartridge cases and fred pro- explosive primer that ignites the cartridge. jectiles (Section 7.1.3.3) are the primary As the name implies, the centre-fre cartridge types of forensic frearms evidence recovered has the primer located in the centre of the from crime scenes, the presence of unfred base, whereas the primer within the rim- (live) cartridges is important to forensic fre- fre cartridge has it located around the rim. arms examiners. Live cartridges allow an Projectiles are identifed for ammunition examiner to determine exactly the type of based on the intended functional purpose of ammunition that was used by the frer and the cartridge and the weapon type the cart- can be used for corroborative intelligence ridge is designed for. Projectile shape, dimen- and for test fring to assist in the identifca- sions and material properties affect the tion of a specifc weapon. external (Section 7.1.6) and terminal ballistics (Section 7.1.7) following projectile exit 7.1.3.3 Fired cartridge cases from the barrel. Typically the softer the ma- and projectiles terial property of the projectile, the more easily the projectile will deform on impact Brief examination of fred cartridge cases with a target, increasing surface area and can provide valuable intelligence to the increasing the amount of energy that can be forensic practitioners investigating the inci- transferred into the target material. For ex- dent. Information can include the manufac- ample, a full metal jacketed (FMJ) projectile turer and calibre of the likely ammunition is harder than a metal jacketed hollow-point used, and probable identifcation of the type (HP) that has an exposed lead cavity at the of weapon, its manufacturer and model, using projectile nose. The HP will deform and mush- class characteristics transferred during the room on impact with a target, signifcantly fring process (for example, the shape and reducing penetration depth and increasing dimensions of the fring pin impression). wounding in comparison to an FMJ. This Knowledge of such initial intelligence can makes the FMJ more suitable for military aid the forensic veterinarian in their exam- use and the HP more suitable to law enforce- ination of wounds (Section 7.2). ment and hunting, where only one target The fred ammunition component that needs to be hit. is more commonly encountered by a forensic Air weapons do not utilize a cartridge veterinarian is the fred projectile, which system, as the compressed air supplies the may or may not be located inside the injured force to propel a single lead pellet using com- species. Ideally, the presence of a forensic parably low gas pressure. More lethal frearms frearms examiner or ballistics expert would utilizing cartridge-based ammunition create be very benefcial as they can assist with much higher gas pressures during ignition, wound examination and interpretation and therefore have greater muzzle velocity, and recover any frearms-related evidence; muzzle energy, range and penetration depth. however, the overriding purpose of the veter- However, research has shown that even blank inarian is to preserve life. As a minimum, an fring weapons can be fatal, due to the gas pres- X-ray of the wound should be undertaken, sures released (Demirci et al., 2011). Projectiles as some initial visual analysis of the X-ray Firearms and Ballistics 87

images can provide intelligence to the prac- will not explain these concepts in depth, titioner during their examination. The approxi- but will introduce the various stages that mate dimension of the base of the projectile comprise the ignition of typical modern can indicate the calibre of the weapon, and cartridge-based ammunition. the shape of projectile found may lead to the type of weapon that discharged it. Also, it is 7.1.4.1 Primer possible that the projectile may have frag- mented inside the body; this could be due When the base of the cartridge is struck by to the design of the ammunition component the fring pin, this creates an impression in or because the projectile has struck dense the metal base known as the fring pin im- material within the body; for example, bone. pression. The distortion to the base causes Retrieval of fred projectiles will be covered the case to strike a metal anvil positioned in Section 7.1.8. directly beneath, within the primer unit, thus Although beyond the scope of this chap- creating a spark. The spark detonates the un- ter, submission of fred cartridge cases and stable, explosive inorganic primer producing projectiles to the laboratory for examination a fame jet of approximately 2000°C (Heard, by a frearms examiner can further identify 2008). the specifc weapon that was involved using The primer mixture comprises an microscopic examination of the individual igniter, an oxidizer and a fuel. The igniter is characteristics engraved and impressed into an explosive chemical compound such as the fred ammunition component. Individual lead styphenate or tetrazine (in lead-free am- characteristics are created by unique tool- munition). Barium nitrate is an oxidizer that marks generated on the surface of the weapon aids fame production by providing oxygen components during the component manufac- during the reaction, and antimony sulphide turing process. The toolmarks are randomly is an example of the fuel needed to increase created due to wear of the tool surface used the temperature and length of the fame. to manufacture the component and these The fame is forced through one (boxer toolmarks are transferred to the component primer type) or two (berdan primer type) during the fring process. As they are random fash holes in the top of the primer unit, and unique, the individual characteristics can which provides suffcient thermal energy to be used to identify a specifc weapon compo- ignite the propellant fakes housed in the nent. Even if a frearm is not recovered, exam- main body of the cartridge case. ination of multiple fred cases or projectiles can be used to link shooting incidents to- 7.1.4.2 Propellant gether and identify a single weapon used in one or more incidents, known as an inferred Propellant is compressed grains of organic weapon. materials designed to burn at a controlled rate. In modern smokeless propellant (as op- posed to black powder), nitrocellulose and/ 7.1.4 Internal ballistics or nitroglycerine is the main component. The shape and dimensions of the grains Internal ballistics covers all aspects involv- (ballistic size) and presence/absence of mod- ing the ammunition and frearm from the erators, stabilizers and/or retardant chemicals moment the fring pin strikes the cartridge within or coated on the grain surface(s) can to the point at which the projectile exits the control the burning rate of the propellant. muzzle of the frearm. A range of scientifc As the grains combust, they produce a large concepts underpin internal ballistics, which volume of gas (primarily carbon dioxide include combustion theory, Piobert’s law of and water vapour), which is sealed inside burning, the ideal gas law, laws of thermo- the cartridge case and chamber of the frearm. dynamics, conservation of energy and linear The temperature and pressure builds inside momentum, and Newton’s laws of physics the cartridge, thereby increasing the burn- (Carlucci and Jacobson, 2008). This section ing rate of the propellant and resulting in an 88 R. Bolton-King and J. Schulze

exponential rate of combustion. The initial The precise velocity of the projectile prior rate of combustion is also determined by the to exit will vary to some extent from the am- ratio between propellant volume and case munition manufacturer’s specifcations, de- volume; a greater volume of unflled space pending on the specifcations of the model in the cartridge case will result in a slower of frearm the ammunition is fred from. For combustion rate, as the gas has more space example, for a given cartridge, the tighter the to fll before the pressure can start to rise. ft of the projectile within the barrel bore, the When the pressure is high enough in the cart- greater the level of friction initially acting ridge it forces the projectile(s) free from the against the forward motion of the projectile, cartridge case; this is known as shot start and therefore the lower the muzzle velocity. (Farrar and Leeming, 1983). If the barrel is longer, then frictional force may act for longer. There will also be some vari- 7.1.4.3 Projectile ability from cartridge to cartridge due to the tolerances during ammunition production and At shot start, the projectile(s) starts to travel how the cartridge seats in the breech of the down the barrel of the weapon and accelerates weapon. due to the work done by the high-pressure gas on the entire surface of the projectile 7.1.4.4 Weapon base, which increases energy transferred to the projectile. Due to the increase in space The detonation of the primer, combustion of behind the projectile, the pressure is still the propellant and friction generated (typic- rising, but the propellant starts to burn at ally for rifed barrels) between the barrel and an increasingly slower rate. Peak pressure the projectile will transfer thermal energy occurs approximately 0.5 ms after cartridge to the metallic frearm components, primarily ignition and can be in excess of 300 MPa the chamber and barrel. Lawton (2001) indi- (Warlow, 2011). cates barrel bore temperatures in the region If the barrel is rifed (see Section 7.1.5.2) of 1100°C, whereas Warlow (2011) suggests then there will be some friction when the over 2200°C. Contact between frearm com- projectile engages with the slightly smaller ponents and ammunition, together with dimension of the barrel bore created by these extreme temperatures, even over such lands of the barrel rifing. Some gas will es- a short period of time, will cause surface cape in front of the projectile through the melting and enhanced wear of the weapon grooves of the rifing as these may be deeper components. than the maximum diameter of the project- When the propellant combusts, the pres- ile. If the barrel is smooth bore and multiple sure of the gases does not only act in the projectiles are fred from the cartridge, as direction of the projectile base, but in all with a shotgun, some gas may escape by directions around the breech of the weapon. passing between and around the shot inside As a result, while the projectile remains inside the barrel. the barrel, the pressure exerted forwards At the time of peak pressure, the pro- on the projectile is experienced backwards jectile may have only moved 2 cm. As the on the weapon, known as recoil. Typically, the projectile accelerates and level of kinetic greater the recoil velocity, the more uncom- energy overcomes the initial frictional force, fortable the weapon is to fre. The production an increasing volume will be left behind the of high-pressure gas or recoil energy gener- projectile and the rate of burning continues ated can be exploited in the weapon design to reduce as the propellant fakes reduce and be utilized by the fring mechanism to in size and produce less gaseous products. eject fred cartridge cases after discharge and Providing suffcient force is maintained as load new cartridges (auto-loading). the propellant burns, the projectile(s) will pass As the pressure acts in all directions, the down the barrel to the muzzle exit within muzzle of the weapon will also lift slightly 2 ms from the strike of the fring pin (War- above its point of aim, especially if the low, 2011). muzzle end of the weapon is unsupported. Firearms and Ballistics 89

Barrel lift will vary depending on the am- 2008) classifes intermediate ballistics as an munition utilized and will ultimately affect area in its own right. The time and distance shooting accuracy. This needs to be con- that intermediate ballistics covers will vary, sidered when sighting the weapon and fr- depending on the type of ammunition used ing in automatic modes. and the ballistic properties of the projectile. This section will briefy discuss how the fow 7.1.4.5 Production of gunshot of gaseous combustion products and presence residue (GSR) of muzzle attachments infuence propellant particles and the motion of the projectile The inorganic primer and organic propellant upon muzzle exit. will not completely burn during ignition of the cartridge. This generates a mixture of 7.1.5.1 Propellant particles and unburnt, partially burnt and still burning gaseous combustion products particles, referred to as gunshot residue (GSR) or frearms discharge residue. GSR will also As previously discussed, high-pressure com- contain some of the metallic particles pro- bustion products escape the muzzle in front duced from the wear of the frearm compo- of the projectile due to the high pressure re- nent surfaces, together with the ammunition lease of gas after shot start, together with a materials removed by striated contact with column of air that is pushed forwards by the the weapon components, such as the barrel. moving projectile. When these high-pressure GSR particles predominantly exit the weapon gases exit the muzzle, a shock wave (precur- once the projectile has left the muzzle, but sor blast shock) is created just in front of the some will escape before the projectile(s) exits muzzle, travelling slightly above 340 m/s and GSR will be carried by the escaping gas- (speed of sound) and meets with the ‘normal’ eous combustion products in gaps between atmosphere. This shock wave generates a the projectile(s) and bore surface. GSR will sonic bang and radiates out in a spherical also exit from any opening within the fre- direction away from the muzzle. arm, such as the ejection port (semi-automatic Precursor bottle shock and the Mach weapon) or cylinder (revolver). disk also occurs around the muzzle as the Partially burnt and still burning particles precursor blast shock is trying to travel are important with respect to intermediate back inside the barrel, against the fow of gas ballistics (Section 7.1.5), as well as being ( Carlucci and Jacobson, 2008). The bottle signifcant to forensic investigation. In the shock increases as the gas velocity increases; context of veterinary forensics, presence or as gas velocity reduces the bottle shock will absence of GSR can assist with determining eventually shrink back inside the barrel. fring distance between muzzle and the tar- When the projectile exits the muzzle, get, differentiating between initial entry and the gas seal is broken and a further release of exit wounds and identifcation of the type highly pressurized gas is released into the of ammunition used (Heard, 2008; Broz˙ek- atmosphere. A second high-pressure blast wave Mucha, 2009; Dalby et al., 2010; Haag and is formed, together with further bottle shock Haag, 2011; Warlow, 2011). and Mach disk. This second blast wave is higher in pressure than the precursor blast wave and is initially non-spherical due to 7.1.5 Intermediate ballistics the projectile and fow of combustion gases. This blast wave accelerates the combus- Intermediate ballistics is a transitional area tion products forwards, creating a turbulent covering the moment the projectile exits the column of gas. The column of gas initially barrel until the projectile is considered to overtakes the projectile, causing a shock wave be in free fight. Heard (2008) encompasses around the base of the projectile (stern shock), intermediate ballistics within the scope of which can accelerate the projectile and pro- wider external ballistics, whereas more spe- duce instability and yawing. The spherical cialized literature (Carlucci and Jacobson, blast shock is travelling faster and has more 90 R. Bolton-King and J. Schulze

energy than the precursor blast shock and the nose to rise or fall above or below the catches up with it; shock waves lose energy projectile’s line of fight base, which increases and velocity as they increase in size and the the surface area presented at the projectile gas molecules dissipate. nose. Such increase in surface area increases Within the gaseous combustion prod- the air resistance around the projectile, redu- ucts, still burning propellant particles are also cing projectile velocity and, without a rota- present. These particles exit from the barrel tional force about the centre of mass, this in front of the projectile, but are predomin- would cause the bullet to tumble. Tumbling antly built up behind the projectile. As these would ultimately reduce projectile velocity, particles pass through high-pressure shock energy, distance (range), accuracy, precision waves, their temperature and burning rate of fre, but increase damage/wound poten- increases producing visible light (incan- tial due to an increased surface area upon descent radiation), known as muzzle fash. contact with the target. Prefash can occur before the projectile exits To counteract destabilization, the rifing the muzzle, but primary muzzle fash occurs inside the barrel consists of spiral lands and at the muzzle of the frearm after projectile grooves. The higher-profle lands on either exit. Intermediate muzzle fash can occur side of the grooves in the barrel bore are further from the muzzle. As the gases in the smaller in diameter compared to the max- bottle shock expand rapidly they cool down imum diameter of the projectile and therefore and a faint muzzle glow can be seen moving engrave into the surface of the projectile, away from the muzzle. gripping the projectile and bringing about Once all the combustion products have rotation as the projectile travels down the been released from the barrel, there is a void barrel. Upon muzzle exit, the projectile will in the barrel bore. As the blast shock radiates be rotating at a pre-defned rate. This rota- out in all directions, the blast wave can then tion helps to re-stabilize the projectile as recede down the empty barrel along with it travels through the turbulent gas due to some of the combustion products. If a target gyroscopic nutation and thus, the rate of is in close proximity to the muzzle upon dis- rifing twist down the barrel is important charge, it is this vacuum effect which sucks for optimum stabilization of the projectile. the target material back inside the barrel, Depending on the muzzle velocity of which can therefore be of forensic signifcance the projectile, the projectile will either not when interpreting the shooting incident. reach the blast wave (subsonic projectile), or overtake the blast shock (supersonic projectile) and generate a shock wave and 7.1.5.2 Projectile audible sonic bang from the nose of the pro- Upon muzzle exit, the projectile is in a tur- jectile. With supersonic projectiles, a further bulent atmosphere and is therefore not fully shock wave and sonic bang will be created stabilized. This can have varying degrees of when the base of the projectile subsequently impact on the projectile, depending on its passes through the blast shock. shape. For example, cannonballs and shot are typically spherical and therefore turbulence 7.1.5.3 Muzzle attachments will affect the object similarly in all directions. Heard (2008) indicates there are six types With most other types of projectile, however, of muzzle attachment for pistols, revolvers, they are designed to be aerodynamic and rifes and shotguns: stable during free fight and may have characteristic features (such as fns) on the surface to 1. Sound suppressors. ensure that the projectile arrives at the target 2. Recoil reducers (compensators). nose frst. 3. Flash hiders. Turbulence created by the combustion 4. Muzzle counter weights (to reduce muzzle products initially destabilizes these projectiles, lift). causing the projectile to yaw slightly (1.5° 5. Grenade dischargers. for a 0.303-in. rife bullet (Heard, 2008)), i.e. 6. Recoil boosters. Firearms and Ballistics 91

Only the frst three will be discussed here, 7.1.6.1 Muzzle velocity and kinetic energy as these have a direct infuence on intermediate ballistics. During internal ballistics, approximately Sound suppressors are predominantly 30% of the energy created is actually trans- designed to reduce noise generated from an ferred to the projectile(s) (Warlow, 2011), expanding gas pressure wave by 18–32 dB predominantly in the form of kinetic energy, (Heard, 2008). They also act to reduce fash resulting in acceleration of the projectile(s) and recoil to some extent. Such attachments to a known velocity. Following muzzle exit lower the energy of the gas by allowing the and a very short distance past the muzzle, gases to expand within a closed container, the projectile reaches a maximum velocity, by increasing the volume the gas fows into referred to as muzzle velocity. Muzzle vel- or by making the gas do mechanical work ocity is pre-determined by the ammunition (moving a rotor, for example), or by reducing manufacturer; however, as previously ex- the temperature through absorption. Those plained, fred projectiles may not reach the suppressors that are built into the barrel can technical specifcation of muzzle velocity also reduce the muzzle velocity of the pro- quoted by the ammunition manufacturer. jectile to less than the speed of sound, Kinetic energy and muzzle velocity are thereby preventing the supersonic boom of two of three linked factors; the third compo- fring by bleeding off some gas near the muz- nent that affects muzzle velocity and the zle of the weapon. kinetic energy is the projectile mass. Kinetic Recoil reducers (or muzzle brakes) are energy is calculated by squaring the vel- designed to direct the muzzle gas sideways ocity and then multiplying this by half the rather than in a primary forwards motion. mass of the projectile. As the mass of the Gas defection is obtained by placing one or projectile increases, a greater amount of more sets of symmetrical ports along the work, force and energy is required to move sides of the muzzle attachment for gases to the projectile the same amount. Therefore, escape. for two projectiles of different masses to Modern fash hiders are usually the sim- have the same muzzle velocity, more kinetic plest type of muzzle attachment. These energy (and therefore a higher gas pressure) devices are primarily designed to reduce is required to fre the heavier projectile. intermediate muzzle fash by dispersing the A projectile with higher mass will ultimately muzzle gas and breaking up the barrel shock enhance its ‘carrying power’ (Heard, 2008). and Mach disk. They are usually cone-shaped, When considering terminal ballistics a tube with odd-numbered slots, or a bar later on, the kinetic energy of the projectile style (Farrar and Leeming, 1983; Carlucci is of greater importance than the velocity of and Jacobson, 2008). the projectile, as kinetic energy takes into account both projectile mass and velocity. It is also the ability of the projectile design to transfer energy to the other object that im- 7.1.6 External ballistics pacts on the resulting damage to the object. As soon as the projectile exits the muz- External ballistics covers the period of zle, the energy and force acting on the pro- fight from the point at which the projectile jectile is in the forwards (horizontal) direc- is stable and behaving within ‘normal’ at- tion away from the muzzle, therefore the mospheric conditions until the moment it velocity vector has a positive value. Initially comes into contact with an object. Like this will be the dominant direction of force internal ballistics, this aspect is very com- acting on the projectile. However, unless plex and involves extensive mathematical the projectile is fred into a vacuum, there computation to determine a projectile’s fight will always be forces acting against the pro- path. This section considers basic concepts jectile in the opposite direction limiting the that critically underpin this area of applied forwards progression, reducing the kinetic physics. energy and therefore the velocity of the 92 R. Bolton-King and J. Schulze

projectile over time. These opposing forces a long, sharp and low-angled nose (spitzer) to are from the interaction with molecules reduce the cross-sectional surface area ini- within the atmosphere; the phenomenon is tially presented to the air and may even have known as air resistance (drag). The forward a slightly angled base (boat-tail) to improve movement of the projectile compresses the the fow of air particles and reduce turbulence air molecules in front of it causing areas of from air molecules behind the projectile. higher pressure which act in all directions The term ballistic coeffcient is used to cal- around the front of the projectile. Minimiz- culate the decline in projectile velocity due ing the cross-sectional area of the projectile to the air, and takes into account projectile and making the projectile less angular will mass and diameter (Carlucci and Jacobson, reduce air resistance. The air molecules then 2008). Typically, the higher the ballistic fow around the projectile, a small amount coeffcient, the better a projectile retains its of surface (skin) friction is created between velocity over time. Using data provided by the air molecules and the sides of the pro- Forker (2010), Table 7.1.2 and Fig. 7.1.2 jectile, further reducing the kinetic energy illustrate how the projectile energy changes and velocity of the projectile. for some common cartridges. When the air molecules have passed over the sides of the projectile, they have to fll in the space left by the base of the project- 7.1.6.2 Trajectory ile. This again causes high-pressure regions at the back edges of the projectile and leaves Air resistance is not the only force acting on a turbulent wake of gas behind the project- the projectile. Acceleration due to gravita- ile. The shape of the nose and base of the tional pull from the Earth is constantly act- projectile are therefore critical to limiting ing downwards in the vertical direction on the effect of air resistance on the kinetic en- the unsupported object at 9.81 ms–2 (Haag ergy and velocity of the projectile. A more and Haag, 2011). As a result, the natural aerodynamically shaped projectile will fight path or trajectory will always ultim- exhibit a slower decline in velocity and ately curve downwards towards the ground kinetic energy due to air resistance. Aero- (bullet drop), unless the trajectory is prema- dynamically shaped projectiles will display turely interrupted by an object.

Table 7.1.2. Examples of various cartridges.

Bullet Muzzle Muzzle Firearm Projectile Weight G1 Ballistic Velocity Velocity Type Cartridge Manufacturer Type (g) Coefﬁcient (fps) (m/s)

Revolver 0.357 Magnum Sellier and FMJ 158 0.154 1263 385 Bellot Pistol 0.45 ACP American Eagle FMJ 230 0.178 890 271 (Federal) 9×19 mm Sellier and FMJ 115 0.102 1280 390 Bellot Riﬂe 0.22 Hornet Sellier and FMJ 45 0.102 2346 715 Bellot 0.223 Remington American Eagle FMJ 55 0.270 3240 988 (Federal) Boat-tail 0.303 British Sellier and FMJ 180 0.564 2438 743 Bellot 0.458 Winchester Hornady DGX 500 0.295 2260 689 Magnum 7.62 mm NATO American Eagle FMJ 150 0.409 2820 860 (Federal) Boat-tail Firearms and Ballistics 93

(a) 8000

7000

6000

(J) 5000 gy

4000

3000 ojectile ener Pr 2000

1000

0 0 100 200 300 400 500 600 700 800 900 Distance from muzzle (m)

0.22 Hornet (FMJ) 0.458 Winchester Magnum (DGX) 0.223 Remington (FMJ Boat-tail) 0.303 British (FMJ) 7.62 mm NATO (FMJ boat-tail)

(b) 800

700

600 y (J) rg

500

ojectile ene 400 Pr

300

200 02550751000 125150 175 Distance from muzzle (m)

0.357 Magnum (FMJ) 0.45 ACP (FMJ) 9×19 mm (FMJ)

Fig. 7.1.2. Projectile energy changes for some common cartridges. 94 R. Bolton-King and J. Schulze

The initial projectile trajectory will be projectiles are most infuenced by wave affected by the muzzle fring angle (angle of drag, and therefore the nose of supersonic inclination). However, it is typical for the projectiles needs to be designed to minim- projectile not to exit the muzzle aligned ize drag. with the bore so it will experience vertical Angle of inclination has a signifcant role and lateral jump (Carlucci and Jacobson, in the maximum potential range of fre for a 2008) caused by air resistance. Considering projectile. For a specifc projectile fred in a only the effect of vertical gravitation force vacuum on Earth, the time spent in free fight on a projectile fred in a vacuum at 45°, for for the same ammunition will be identical, but example, the trajectory would be a symmet- the maximum range will be obtained when rical parabolic curve about a peak height. there is as much forwards motion as vertical In atmospheric conditions, this para- motion. Maximum theoretical range will bolic curve is no longer symmetrical due to therefore occur at 45° inclination due to the the effect of air resistance (wave drag, base trajectory’s symmetrical shape; 30° and 60° drag and skin friction). The forces counter- fring angles will result in identical, but acting the forward motion of the projectile reduced, range of fre compared to 45°. will cause the projectile not to reach as high Considering the impact of fring angle vertical distance or as long horizontal dis- alone in atmospheric conditions, maximum tance (range). The velocity of the projectile range will typically be generated when fred will reduce over the time of fight at an ex- between 27° and 30° (Carlucci and Jacobson, ponential rate; therefore, the faster the muz- 2008), although Haag and Haag (2011) indi- zle velocity of the projectile, the greater the cates 30° to 35° for handgun cartridges. The velocity lost per unit of time. accent of the projectile to peak height will Many frearms are discharged at relatively be slightly lower and of less distance com- low-angle (fat) trajectories over relatively pared to in the vacuum, but the biggest effect short range; however, when the target is to range occurs during projectile descent to positioned at a signifcant range or the pro- ground. Pistol and revolver bullets, when jectile needs to travel over obstacles in the fred at their optimum departure angle can line of sight, higher angles of trajectory are reach a maximum range of 1000–2000 m, employed, exploiting the curved trajectory. whereas rife bullets can reach between 3000 m and 4000 m (Haag and Haag, 2011). Shot need to be considered separately. 7.1.6.3 Range Shot are spherical, symmetrical and do not require stabilization by rotational force. Maximum effective range of real projectile Spheres are less aerodynamic, and these trajectories can be diffcult to calculate. projectiles are not designed to be fred over Range is affected by the muzzle velocity, the long distances. Their maximum range in air mass, shape and cross-sectional area of the has been demonstrated to be 1–3% of the projectile. Other effects include altitude, range achieved if fred in a vacuum (Chugh, barometric pressure, crosswind, humidity 1982) compared to approximately 20% for and temperature. However, to consider the bullets. As there are multiple projectiles, effects of all these variables is outside the shot spread out over range and can be used scope of this chapter. more effectively for distance determination As velocity is calculated by dividing (Çakir et al., 2003; Haag and Haag, 2011). distance by time, the greater the velocity of the projectile, the further the projectile will 7.1.6.4 Accuracy and precision travel in a set period of time. To maximize range, the aerodynamic shape and geometry The accuracy (closeness to the intended point of the projectile are critical depending on of impact) and precision (spread around the projectile muzzle velocity (subsonic or super- intended point of impact) of the projectile sonic). Subsonic projectiles are most infu- will be affected by the frer, weapon and at- enced by base drag, whereas supersonic mospheric conditions, including wind speed Firearms and Ballistics 95

and direction, the extent of which is outside bullets) are designed to mushroom at the nose the scope of this chapter; however, some to increase surface area and increase the examples are considered. transfer of energy from the projectile to the The weapon type is important to con- target. The consequence is a greater damage/ sider. Handguns are typically designed for wounding potential. FMJ projectiles, how- close combat and therefore less accurate and ever, are not designed to deform on impact precise over distance than rifes. Generally, and therefore do not transfer as much energy this is due to the shorter barrel and less aero- into the target, ultimately reducing the dam- dynamic projectiles. By design, shotguns fr- age/wound potential and increasing the depth ing a number of shot are primarily used for of penetration into the target. hunting and therefore accuracy and preci- The angle at which the projectile hits sion are less critical as there are multiple shot the target also affects whether the projectile that spread out as range of fre increases, and is more likely to penetrate into the target or therefore the shot are more likely to pene- ricochet, i.e. defect off the target surface. trate and strike the animal. For every combination of specifc projectile Firing a brand new weapon from a design and target surface, there will be a fxed fring position should provide excel- critical angle that determines whether the lent accuracy and precision. Over time, as projectile penetrates or has the potential to weapon components such as the barrel suf- ricochet. Generally, the critical angle will be fer from wear, the tolerance to generate a relatively low (oblique) and the projectile stable projectile during fight increases typically ricochets off at a comparably and this has a negative effect on accuracy lower angle (Haag and Haag, 2011). and precision. Incorrect support, hand- The effect of ricochet and tumbling will ling and aim of the weapon during fring affect the size and shape of penetrating (Goonetilleke et al., 2009) will reduce ac- wounds (Section 7.2). Tumbling or instabil- curacy and lower precision due to recoil ity in a projectile will cause it to yaw. If the forces, whereas reducing the trigger pull projectile hits an animal in a state of yaw force required to action the trigger mechan- rather than perpendicular and nose frst, ism and discharge a round can increase the surface area where impact occurs is in- precision and accuracy. creased and therefore the size of the entry wound may be increased. Such impact angle can also transfer energy into the animal/target more effectively. However, 7.1.7 Terminal ballistics if the projectile is designed to transfer energy effectively (for example, a hollow- Energy and design of the projectile as well point or soft-point) then the energy trans- as the density, material properties and sur- fer may be less effective as the nose will face roughness will affect what happens to not be able to perform as designed. the projectile when it hits a target surface. Target materials that are less dense and more malleable than the projectile mater- 7.1.8 Retrieval of ﬁred ammunition ials are more likely to deform, be pene- components trated to some extent and absorb more energy from the projectile, compared to those 7.1.8.1 Cartridges and ﬁred that are denser and have greater hardness. cartridge cases Yielding surfaces that deform upon impact produce greater angles of projectile rico- If you are called to a crime scene of a sus- chet than unyielding surfaces (Haag and pected shooting, the forensic veterinarian Haag, 2011). should be aware of the potential for fnding The design of the projectile will have live ammunition as well as fred cartridge an effect on the potential for ricochet. Some case evidence. Depending on the nature of projectiles (e.g. soft-point or hollow-point the scene and the location of the incident 96 R. Bolton-King and J. Schulze

geographically, there will be a variety of (Wightman et al., 2013) and the thickness policies governing who recovers this phys- and material properties of their skin will in- ical evidence. The purpose of this section is fuence the ability for the pellet to pene- to remind the practitioner that such evidence trate, together with the energy and shape of has forensic value in inferring the calibre the projectile. and type of frearm likely to have discharged As previously stated, any fred project- the cartridge, the number of weapons in- iles recovered should be handled with plas- volved, and has the potential to link crimes tic tweezers or forceps to prevent damage to utilizing discharge of the same weapon in the forensic characteristics. Upon recovery various cases; and microscopic examination of the projectile, this should be washed with of fred cartridge case evidence can uniquely sterile water to remove biological hazards identify the frearm that discharged it, if a (different protocols are required for project- weapon is ultimately recovered. ile retrieval from humans) and air-dried If unfred ammunition is discovered, before packaging, to prevent any corrosion the cartridges need to be recovered using of the projectile material surface. Packaging good practice to minimize contamination, for fred projectiles is ideally in polythene such as wearing gloves, and should be pack- and plastic containers, i.e. not containing aged separately to any weapon recovered to cotton wool. minimize risk and prevent accidental fring. Wadding components within shotgun Cartridges should be packaged in paper bags, cartridges are ejected from the cartridge along cardboard boxes or plastic containers (Tilstone with the single slug or multiple shot. This et al., 2013) lined with non-abrasive material can travel over 30 m from the muzzle of the (not cotton wool) to prevent them rolling weapon (Bonfanti and De Kinder, 2013) and, around during transportation. therefore, fnding wadding inside a wound If fred cartridge cases, shotgun wad- tract or permanent cavity can imply that ding (typically made of fbre or plastic) and/ the weapon has been discharged at close or projectiles are observed in the scene sur- range to the target. Recovery and packaging roundings they should be recovered using of shotgun wadding should be as described plastic forceps or tweezers, to prevent dam- above for fred projectiles. age to the evidence surface (Bruce-Chwatt, 2010). Handling items with metal tweezers 7.1.8.3 Gunshot residue (GSR) of a harder material than the evidence may cause permanent toolmarks on the evidence GSR can be sampled with commercially surface, that could damage or impede foren- available GSR collection kits by swabbing sic examination and interpretation subse- around the area of the wound entry. GSR quently undertaken by frearms examiners. may be differentiated from other metallic Fired cartridge cases, like the cartridges residues (Romolo and Margot, 2001; Dalby themselves, should be packaged as they are et al., 2010; Grima et al., 2012) and can recovered from the scene in paper bags, sometimes be uniquely identifed to a type cardboard boxes or plastic containers lined of ammunition (Brozek-Mucha and Jankow- with polythene/non-abrasive material (not icz, 2001); for example, if the composition cotton wool), with the latter preferably used of the primer is very distinctive. GSR can be for fred projectiles and wadding. indicative of close range of fre (Ditrich, 2012), as can the presence of stippling, pow- 7.1.8.2 Fired projectiles and der tattooing on the skin and burning of hair shotgun wadding from burning propellant fakes and hot gases released from the muzzle of the frearm. Fired projectiles, such as bullets, pellets (air However, if an air weapon was utilized, such weapons), slugs or shot (shotgun) may be characteristics will not be present around present in the animal. Even legal unlicensed an entry wound, even at close proximity, as air weapons can penetrate animal skin, but there is no combustion of propellant used to research has shown that the type of animal propel the pellet out of the weapon. Firearms and Ballistics 97

7.1.9 Conclusion computer tomography (CT) and ultrasound, should be employed at the earliest oppor- This section aimed to introduce some of tunity. Use of such technologies facilitates the key scientifc principles underpinning the formation of the forensic examination shooting incidents that may influence strategy by providing visualization of bullet- observed wounding in animals. Variations wound channels, projectiles or projectile in the type of frearm and ammunition (in- fragments, and the presence of fractures and ternal ballistics) used in the shooting as other damage in the animal prior to invasive well as environmental conditions and shoot- action. ing distances (external ballistics), location Firearms evidence collated from both of impact, composition of the target mater- the crime scene and the injured animal can ial and design of the projectile upon impact provide vital information and intelligence (terminal ballistics), for example, may all to those investigating both domestic animal cause variations in the expected severity of and wildlife crimes. The form and extent of damage and lethality. By understanding frearms evidence that may be located at a how these factors may affect wounding, po- crime scene will also vary, depending on tential forensic veterinarians may have an the frearm, ammunition and ballistic vari- increased capacity to interpret the manner ables. Correct handling and recovery of in which injuries have been sustained and such evidence is important for any further provide further information to the forensic analysis requested to be probative in the investigative process. case. Demonstration of the breadth of know- The essential steps in the forensic exam- ledge required to investigate shooting inci- ination and investigation of a shot animal dents may highlight the need for forensic were identifed, clearly highlighting the veterinarians to get in contact with subject requirement for a logical and methodical experts to provide support prior to and dur- approach supported by extensive documen- ing forensic examinations and any subse- tation. The approach for animals should be quent investigation. By building a strong similar to that conducted on humans and all prosecution case, including corroborative wound ballistics research may be relevant evidence from frearms examiners, investi- for consideration in application to animal gators are more likely to be able to link practice. It is vital for external observations crime series and identify those involved in to be completed before invasive internal the crimes, to ultimately increase the prob- examination commences, and modern non- ability of prosecution and conviction in fo- invasive imaging technologies, including rensic cases.

References

AFTE Training and Standardization Committee (ed.) (2007) Glossary of Association of Firearms and Tool Mark Examiner, 5th edn. AFTE, Montreal, Canada. Available on CD-ROM. Berman, G. (2012) Firearm Crime Statistics. SN/SG/1940. House of Commons, London, UK. Bolton-King, R.S. (2012) Classification of barrel rifling transitions for the identification of firearms. PhD thesis. Nottingham Trent University, Nottingham, UK. Bonfanti, M.S. and De Kinder, J. (2013) Shotgun ammunition on a target. In: Siegel, J.A., Saukko, P.J. and Houck, M.M. (eds) Encyclopedia of Forensic Sciences. Academic Press, Waltham, Massachusetts, USA, pp. 48–53. Broz˙ek-Mucha, Z. (2009) Distribution and properties of gunshot residue originating from a Luger 9 mm ammunition in the vicinity of the shooting gun. Forensic Science International 183(1–3), 33–44. Brozek-Mucha, Z. and Jankowicz, A. (2001) Evaluation of the possibility of differentiation between various types of ammunition by means of GSR examination with SEM–EDX method. Forensic Science International 123(1), 39–47. Bruce-Chwatt, R.M. (2010) Air gun wounding and current UK laws controlling air weapons. Journal of Forensic and Legal Medicine 17(3), 123–126.