MODULE 2

MODULE 2: BRANCHES OF BALLISTICS

1. INTERNAL BALLISTICS

• Definition: Study of a projectile's behavior from ignition of propellant to its exit from the firearm.

• Importance: Key for designers and users of firearms (e.g., rifles, pistols, artillery).

• Key Processes:

  • Firing Mechanism:

    • Firing pin strikes cartridge, marking it distinctly.

    • Explosive pressure causes bullet to expand and fill rifling grooves, creating spin.

  • Significance of Marks: Unique marks left on bullets indicate the firearm used.

  • Indicators of Use: Presence of rust or cobwebs indicates lack of recent firing.

  • Wounds and Residues: Particles may lodge in the barrel from wounds at close range.

Priming Method

• Steps to fire a firearm:

  • A. Firing pin strikes the primer.

  • B. Ignition of priming mixture occurs.

  • C. Combustion of gunpowder leads to:

    • D. Expansion of heated gases.

    • E. Pressure developed (measured in psi - pounds per square inch).

    • F. Energy generated (measured in foot-pounds - capacity to lift one pound at one foot height).

    • G. Recoil occurs after explosion (rearward movement of firearm).

    • H. Bullet velocity measured in feet per second (ft/sec).

• Bullet Rotation: Depends on the twist of rifling, engraves markings on cylindrical surfaces of the bullet as it travels.

2. EXTERNAL BALLISTICS

• Definition: Study of the projectile's motion after exiting the gun muzzle.

• Key Concepts:

  • Bullet behavior from muzzle exit until striking a target, including direction and velocity.

  • External factors: Air resistance, sectional density, bullet shape.

Bullet Motion Parameters

• A. Muzzle Blast: Sound produced at muzzle after explosion.

• B. Muzzle Energy (ME): Energy post-bullet exit from firearm.

• C. Trajectory: Curved path followed by the bullet in flight.

• D. Range: Distance between firearm and target:

  • 1. Effective Range: Max distance for lethal impact.

  • 2. Maximum Range: Greatest distance at optimal elevation.

• E. Velocity: Speed of the bullet.

• F. Air Resistance: Opposing force supplied by air molecules that slows the bullet, affecting its trajectory.

• Effect of Gravity: Pull of gravity causes downward movement of the bullet.

Factors Influencing External Ballistics

• • Drop: Bullet's descent caused by air resistance and gravitational pull.

• • The noise of sonic tearing occurs when bullet velocity exceeds the speed of sound (approx. 1100 ft/sec).

• • To suppress sound, bullets must travel below sonic speeds, leading to more drop and reduced effectiveness at long ranges.

3. TERMINAL BALLISTICS

• Definition: Study of the bullet's impact effects upon target.

• Factors Examined: Changes in trajectory and speed on impact, penetration, wound shape, tissue damage.

• Techniques: CT scanning for examining bullets that can't be removed.

Terminal Parameters

• A. Terminal Accuracy: Bullet grouping on target.

• B. Terminal Energy: Energy delivered by bullet.

• C. Terminal Velocity: Speed upon impact.

• D. Terminal Penetration: Depth achieved in target.

Hydrostatic Shock

• Theory: Wounding effects produced by shock waves in tissues.

• Evidence: Observations of fruit exploding due to bullets illustrate this phenomenon.

• Application: Damage can occur to vital organs by hydrostatic shock, particularly with high-velocity cartridges.

4. FORENSIC BALLISTICS

• Definition: Branch of ballistics focused on field investigation and examination of firearms evidence.

Key Functions of a Firearm Examiner in Forensic Ballistics

• A. Field Investigation: Collecting, marking, preserving, and transporting firearms evidence.

• B. Technical Examination: Evaluating bullets and shell casings, determining if they were fired from suspected firearms.

• • Reports generated include testimonies in court.

• C. Legal Procedures: Presenting ballistic reports and evidence in court.