Types of ballistics
- Internal ballistics
- External ballistics
- Terminal ballistics
Rifled firearm
- Cross section: lands and grooves
- Fired as a single bullet
- No contact with each other on firing
- Composed of lead
- Rotation present ➡️ increase in:
• velocity
• energy
• gyroscopic moment
• range
Caliber of a rifle
Distance between 2 opposite lands in the cross section of a rifle
Smooth bore weapon
- Smooth Internal surface
- Pellets strike each other
- Composed of lead, antimony
- Rotation absent: less velocity, range
Example:
shot gun - 40-50 yards
Ranges of rifles
Revolver: 200
Pistol: 400
Military rifle: 1000-3000
In yards
Modifications of smooth bore weapon
- Choking:
Funnel shaped muzzle ➡️ reduce dispersion of pellet - Paradoxing:
Terminal part has lands and grooves
12 and 24 bore gun
In a 12 bore gun, lead sphere of 454 gm is equally divided into 12 pellets
Similarly is for 24 bore gun
Cartridge of a rifled firearm
The trigger removes the detonator cap,
When primer is ignited (friction) ➡️ gun powder burns ➡️ pressure increases ➡️ bullet fired (or pellets)
Cartridge of a smooth bore weapon consists of
- Pellets
- Felt wad - lubricant
- Gun powder
- Card board disc
- Detonator cap or percussion cap: Cu or Zn
Composition of primer
B. Barium nitrate
L. Lead
As. Antimony Sulfide
T. Tetracene
Types of gun powder
1. Black gun powder: KNO3 - 75% oxidising Charcoal - 15% binding Sulphur - 10% fuel 2. Smokeless gun powder: better • single base - nitrocellulose NC • double base - NC + nitroglycerin NG • triple base - NC + NG + nitroguanidine 3. Semi smokeless gun powder: 20% smokeless \+ 80% black gun powder
Types of black gun powder
Fg, FFg, FFFg
F - fineness
More the number of F, faster is the burning of the powder
Tests for detection of gun powder
H. Harrison Gilroy test
A. Atomic absorption spectroscopy
N. Neuron activation analysis
D. Dermal nitrate test/ paraffin test- not used
SEM-EDXA Scanning Electronic Microscope - Energy Dispersive X-ray Analysis
Bullets are picked up by
Hand (with gloves🧤) and not by any other instrument to preserve markings
Markings of a bullet
1. Primary markings: Decides class Decided by manufacturing company 2. Secondary marking: Individual irregularity of weapon barrel Bullet fingerprint
Types of bullet
Part 1
1. Dum Dum bullet: maximum damage Terminal end broken/ chiseled out ➡️ explodes Sometimes jacketed 2. Express bullet: high velocity Base has a hole 3. Tracer bullet: Release powder throughout is course 4. Incendiary bullet: contains phosphorus
Types of bullet
Part 2
- Frangible bullet: fragments
- Glancing bullet:
Grazes objects causing gutter fracture - Souvenir bullet:
Restrained billet lodged in bone or soft tissue
Lead poisoning - Ricochet bullet:
Oblique entry wound
Types of bullet
Part 3
9. Yawning bullet: slow and irregular Keyhole shaped entry wound 10. Tumbling bullet: tumbles on end 11. Tandem bullet: piggyback bullet Two bullets fired simultaneously Second bullet pushes the first 12. Plastic bullet: Baton bullet PVC
Billiard ball effect
Pellets when they strike each other
Tandem cartridge
Single cartridge having 2 bullets ➡️ 2 entry wounds
Differences between entry and exit wound for both rifles and shotguns
- Size: entry - small
exit - large (except point blank) - Margin: entry - inverted
exit - everted - Tissue discolouration only in entry wound - cherry red (CO from smoke and Hb)
- Singing, blackening and tattooing are seen only entry wound
- Skull bone bevelling
Features of an entry wound specific to rifle
1. Grease collar: Due to lubricant surround the entry wound 2. Abrasion collar: Surrounding the grease collar Decides the direction of the bullet
Shape of entry wound of a shotgun
Contact shot: stellate or cruciate O. Oval/ circular: 0 - 1m R. Rat hole: 1 - 2m Indented margins S. Satellite: 2 - 4m Major entry wound surrounded by many minor wounds Distant: more than 4m Individual pellet entry wounds
Features of a point blank shot
Entry wound:
Larger
Satellite or cruiciate shape
Muzzle markings may be seen
