Forensic Ballistics Study Notes

Forensic Ballistics

Instructor Details: Tolu Abejide
Email: t.abejide@derby.ac.uk
Course Code: 5FO509

AIRGUNS

Airguns are often categorized as popular sporting and working guns. They can be purchased by anyone aged 18 years and older without the requirement for a certification, provided they meet specific criteria noted in the 1969 regulations.

Legal Definition and Specifications

According to The Firearms (Dangerous Air Weapons) Rules 1969, the definitions that govern airguns include:

  • Air pistols: any air pistol that has a muzzle energy below 6 foot-pounds (ft-lb) or 8.2 Joules.
  • Air rifles: any air rifle that has a muzzle energy above 12 foot-pounds (ft-lb) or 16.4 Joules.
    Airguns are significant in criminal investigations due to their implications on legality, lethality, and potential for criminal damage. A fundamental question often arises: Are airguns considered firearms? This question necessitates a careful examination of their specifications and legal definitions.

OPERATION MECHANISM

Airguns operate through various mechanisms categorized as follows:

  • Spring powered
  • Gas ram powered
  • Toggle lever (“Pump up”)
  • Single-stroke pneumatic
  • Pre-charged pneumatic (PCP), which can use CO2
  • Gas Blowback (HFC/Propane)
  • BB guns

Spring Powered Airguns

Spring powered airguns are characterized by their affordability and ease of production, making them prevalent at the lower end of the market. The mechanism involves air being compressed by a piston that is driven by a spring.

Key Mechanisms
  • Barrel Cocking
  • Under Lever
Components
  • Cocking Rod/Link
  • Spring
  • Cylinder
  • Piston
  • Breech port
  • Transfer port
    The operation of these airguns involves a swept volume of the air that moves within their cylinder.

Gas Ram Powered Airguns

Gas ram powered airguns function similarly to spring powered models but eliminate certain idiosyncrasies associated with spring and piston mechanisms.

Operational Mechanism
  • Uses a piston system that contains compressed gas, mostly nitrogen.
Components
  • Gas Ram Unit
  • Non-return valve
  • Transfer port
  • Cylinder valve

Toggle Joint “Pump Up” Airguns

In toggle joint airguns, a manually operated piston compresses the air to fill a reservoir. This model (multi-stroke) utilizes the entirety of the air charge when discharged.

Single Stroke Pneumatic Airguns

These airguns compress a small volume of air in a single action, typically resulting in lower power but offering good consistency between shots.

Pre-charged Pneumatic (PCP) Airguns

Pre-charged pneumatic airguns boast integrated or detachable air reservoirs enabling multi-shot capability.

Features
  • Gas regulators maintain shot-to-shot consistency, making them popular in competition settings.
  • They are complex to manufacture and typically more expensive.
Specifications
  • Operates under high pressure, utilizing compressed air cylinders at approximately 200-300 bar.
Components
  • Air reservoir
  • One-way fill valve
  • Transfer port
  • Exhaust valve
  • Hammer

CO2 Powered Airguns

These airguns utilize disposable canisters filled with compressed CO2, commonly found in 12 g and 88 g sizes.

Characteristics
  • They are generally less powerful than PCP airguns and are also available at a lower price point, although advanced target rifles have emerged.
  • CO2's volatile nature can lead to less consistent performance.

Gas Blowback Airguns

These airguns utilize propane or HFC gas, which is charged into a reservoir in the magazine.

Functionality
  • This gas is regulated and used to propel BBs, providing low-power, multi-shot capabilities.
  • They also facilitate ‘self-loading’ and ‘automatic’ action in specialized airguns, such as Airsoft.

BB Airguns (Airsoft)

These airguns can use spring, gas, or electric mechanisms to fire plastic BBs.

Design
  • Often constructed using brightly colored or transparent materials, enhancing safety and visibility.

Airgun Pellets

Airgun pellets are highly specialized projectiles, and their design is crucial for the effective functioning of airguns.

Pop Quiz

Questions

Is this air rifle a firearm?

  • What is the definition of a firearm?
  • How do we determine whether it is a firearm?
Answers

According to Section 57(1) of the Firearms Act 1968 (as amended): "a lethal barreled weapon of any description from which any shot, bullet or other missile can be discharged."

Questions and Further Inquiries

For additional questions, please contact Tolu Abejide at t.abejide@derby.ac.uk.
Website: derby.ac.uk