Introduction to Forensic Ballistics

Introduction to Forensic Ballistics

• 1.
  INTRODUCTION TO BALLISTICS
• 2.
  WHAT IS AFIREARM? An instrument or device capable of propelling a projectile or a charge consisting of number of projectiles with sufficient velocity using as propellant the force of expansion of gases generated by burning of black power or smokeless powder.
• 3.
  REVOLVER: PARTS
• 4.
  SELF LOADING RIFLE
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  SHOTGUN
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  WHAT IS ANAMMUNITION? An assembly which creates power in a firearm (or a gun or a weapon or, say, small arm). The firearm uses this power and discharges a projectile or a charge consisting of a number of projectiles at high velocity in any desired direction.
• 7.
  WHAT IS AAMMUNITION? An assembly of three components: 1. Primer 2. Propellant 3. Projectile(s) (Bullet) A firearm could also be defined as a thermodynamic device for converting the thermal energy stored in a propellant into the kinetic energy of the bullet or a charge of shots.
• 8.
  WHAT IS BALLISTICS? Ballistics is the science dealing with motion, impact, launching, flight behavior and effects of projectiles .  This subject has been divided into various branches.  Interior ballistics  Exterior Ballistics  Terminal Ballistics  Principles of all these branches have been used in crime investigation and this subject is known as “Forensic Ballistics”.
• 9.
  CARTRIDGE CASE Various componentsof ammunition may be assembled in a container. The whole assembly is called ‘Cartridge’ and the container is called ‘Cartridge Case. This is also known as ‘fixed ammunition’. Thus, a modern cartridge has four main components: - The cartridge case – sometimes also called ‘shell’ or ‘empty’. The primer. The propellant also called ‘powder. The projectile – it may either be a single bullet or a charge of shots where wads are also included.
• 12.
  CARTRIDGE CASES There aretwo types of cartridges: - a) Shotgun cartridge b) Rifle cartridge
• 13.
  CARTRIDGE CASES The cartridgecase serves two purposes. 1. Firstly, it serves as a container and provides water proof container for propellant 2. Secondly, it serves as a gas seal and prevents any escape of propellant gases into the action of the firearm.
• 14.
  THE NOMENCLATURE OFA CARTRIDGE CASE A letter ‘code’ which represents the manufacturer, a date stamp and a calibre. The right hand case therefore is made by RG (Royal Ordnance Factory, Radway Green, UK), in 1942. The middle case was made by I.C.I. , otherwise known as Kynoch in Standish, UK which is represented by the K2, in 1944. Known as the headstamp
• 15.
  CARTRIDGE CASE HEADS •Rimmed • Rimless • Belted • Semi-Rimmed • Rebated.
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  CARTRIDGE CASE HEADS •Rimmed • Rimless • Belted • Semi-Rimmed • Rebated.
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  CARTRIDGE CASE HEADS
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  CARTRIDGE CASE HEADS
• 19.
  CARTRIDGE CASE TYPES 1.Straight cased 2. Bottle-necked 3. Tapered case
• 20.
  PRIMERS • used toignite the powder charge i.e. propellant. • priming mixture contains a sensitive high explosive like mercury fulminate or lead styphnate, a fuel like antimony sulphide and an oxidizing agent like barium nitrate. • The sudden compression of the priming mixture causes the high explosive to produce a lot of heat. It causes the fuel to burn and supplies oxygen for its burning. Thus the sudden compression of the priming mixture gives a very hot flame which ignites the propellant.
• 21.
  PRIMERS: TYPES • Rim-firePrimers: the priming mixture is spun in the folds of the rim of cartridge case. The cartridge case is made of copper or soft brass. • Centre-fire Primers • Shotgun Primers
• 22.
  PRIMING COMPOSITIONS Some ofthe priming compositions used in various countries are as follows: - 1) Lead Styphnate Barium Nitrate lead peroxide Tetracene The early priming compositions were composed largely of mercury fulminate. One such composition consisted of mercury fulminate, antimony sulphide and barium nitrate 2) Lead stypnate Antimony sulphide Barium Nitrate PETN Tetracene Aluminium
• 23.
  PRIMING COMPOSITIONS An improvedprimer composition being considered in USA is SINTOX • Titanium • Zinc Salt • Lead salts
• 24.
  PROPELLNTS The propellants aredefined as low explosives, whose rate of burning is such that the pressure of gases produced by their burning is sufficient for propelling the projectiles in guns. The propellants generally used in small-arms are of the following two types: - i) Black powder or gun powder ii) Smokeless powder iii) Semi-smokeless powder
• 25.
  PROPELLANT • Black powder(gun powder) • The black powder consists of 75% potassium nitrate, 15% charcoal and 10% Sulphur • The burning of black powder yields heavy smoke and a large amount of residue
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  PROPELLANT • The eraof modern high velocity ammunition started with smokeless powders • The basic constituents consist of Nitro Glycerine and Nitro cellulose (gun cotton) • NG is extremely dangerous and cannot be used in pure form. • NC is less sensitive to pressure, develop less heat,
• 27.
  PROPELLANT The smokeless powdersare of two types: i) Single-base powders ii) Double-base powders. The propellants are in the form of small pieces. Each piece is called grain. These grains have shapes like thin flakes, thin spheres, their cylindrical cords, thin disc etc.
• 28.
  PROPELLANT • Semi smokelesspowder is a mixture of black powder and nitro cellulose. • Nitro cellulose: 20% • Potassium nitrate: 60% • Carbon : 12% • Sulphur: 8%
• 29.
  PROPELLANT • A propellantcharacteristic known as “progressivity” is important because it causes increasing gas generation as the propellant burns. • Progressivity can be achieved either by chemical means (via a deterrent coating on the exterior grain) or by geometry (shapes selected because their surface area increases as the grain burns). • Stabilizers are preservatives used to increase storage life. Common stabilizers are found in the diphenylamine family
• 30.
  PROPELLANT MORPHOLOGY • Diskor flake propellants are commonly used in low-pressure, ammunition. Because most of the burn happens from the large flat sides inward, the rate of release is relatively constant until the final stage of the burn cycle.
• 31.
  PROPELLANT MORPHOLOGY • Cylindricalpropellants have greater surface area and fall into the medium to slow energy release category. • Some propellants have cylinders that are solid; others have perforation(s) running parallel to the long axis of the cylinder. • This allows it to burn both from the outside and the inside, keeping the surface area more uniform to achieve and maintain a constant peak pressure
• 33.
  PROPELLANT MORPHOLOGY Form ofnitrocellulose used in small arms cartridges. Ball propellant can be manufactured more rapidly with greater safety and less expense than extruded propellants.
• 34.
  PROPELLANT An ideal powdermust be • Stable on storage • Non-Corrosive • Produce minimum amount of smoke • Produce minimum heat for given velocity • Should be homogenous
• 35.
  PROJECTILES The component(s) ofthe cartridge intended to cause injuries and which are hurled out by the gases produced in the discharge of a firearm • Vary in constructional materials, shapes, size and their ballistics • Lead is the most indispensable and original material: high specific gravity, low melting point, mouldable, comparatively cheaper
• 36.
  PROJECTILES The metal isalloyed with other suitable metals to strengthen them A Lead 90-98% Tin 2-10% B Lead 90% Tin 5% Antimony 5% C Lead 85% Antimony 15%
• 38.
  Bullets are oftenlubricated to reduce friction and prevent oxidation of cases or projectiles. Beewax is placed in the cannelures of the bullet, which attaches itself to the cartridge case
• 41.
  SHOTGUN CARTRIDGE Filled withan appropriate amount of dense powder The powder is covered by a thin compressed over powder wad. Other wads can be cushion wad, under-shot wad, over shot wad