Assignment 05: Classification of Firearms & Rifle vs Shotgun Terminology/Mechanics

1. Classification of Firearms

A. According to the condition of the bore (most important medico-legal classification)

• Shotguns (sporting/breech-loading) - most common
• Muskets (e.g., 0.410 muskets used by police/riot control)
• Muzzle-loading guns (country-made guns) - obsolete, loaded from the muzzle end with propellant, wadding, and shot
• Air/gas and spring guns

• Rifles (air/gas-operated, .22 rifles, military and sporting rifles)
• Pistols (single-shot and semi-automatic/autoloading)
• Revolvers
• True automatic weapons (machine guns/assault rifles)
• DiMaio's Forensic Pathology, 3rd Ed., p. 217-218
• Parikh's Textbook of Medical Jurisprudence, Forensic Medicine and Toxicology, Q.17.6-17.7
• The Essentials of Forensic Medicine and Toxicology, 36th Ed.

B. According to firing action / mechanism

• Bolt action (over-bolt / under-bolt)
• Lever action
• Pump action
• Semi-automatic (autoloading) - one round fired per trigger pull, next round chambered automatically
• Fully automatic - continuous fire as long as the trigger is held

C. According to barrel length (where the weapon is fired from)

• Side arms / hand arms: short-barreled weapons fired from the hand - revolvers, pistols
• Shoulder arms: long-barreled weapons fired resting against the shoulder - rifles, shotguns

D. According to velocity generated (rifled weapons)

E. A simpler modern grouping (DiMaio)

2. Differentiating Rifle and Shotgun: Terminology and Firing Mechanics

Core structural difference

• A rifle has a barrel whose inner surface is cut with spiral grooves called rifling. The metal ridges left standing between the grooves are called lands. The number of grooves usually ranges from 2 to 20 (commonly 4-7), and their spiral turn is called the twist, with the angle of turning called the pitch.
• A shotgun has a smooth bore - the internal surface of the barrel has no grooves at all.
• The Essentials of Forensic Medicine and Toxicology, 36th Ed., "Forensic Ballistics"
• DiMaio's Forensic Pathology, 3rd Ed., "Firearm Basics", p. 214-215

Terminology comparison

Firing mechanics: how each stabilizes and delivers the projectile

1. The firing pin strikes the primer, which detonates the propellant charge in the cartridge.
2. Expanding gas propels the bullet down the barrel.
3. As the bullet travels, the rifling engraves the bullet's surface with the lands, imparting a spin (gyroscopic stabilization) around its long axis.
4. This spin keeps the bullet flying straight and prevents tumbling in air (analogous to the spiral spin on a thrown football), giving rifles greater accuracy, range, and penetrating power.
5. Once the bullet enters soft tissue, the stabilizing spin is lost and the bullet may yaw (rotate off-axis), even flipping to travel base-first if the wound track is long, which increases tissue damage.
6. The characteristic "land and groove" markings etched onto a fired bullet are unique to the firing weapon and are used in forensic identification (class and individual characteristics - caliber, number of lands/grooves, direction and rate of twist).

1. The firing pin/striker detonates the primer in the shot cartridge, igniting the powder.
2. Gas pressure pushes the wad and the shot charge (numerous pellets, or a single slug) down the smooth barrel.
3. Because there is no rifling, the pellets are not spun; they exit the muzzle as a loose cluster that begins to disperse (spread out) almost immediately, and this spread increases with range.
4. The choke (a slight narrowing near the muzzle) partially controls this dispersion, keeping the pellet pattern tighter over a greater effective distance.
5. Lethality at close range comes from the combined effect of multiple pellet perforations plus the concussive blast effect; at longer range, the pellets scatter and lose lethal force rapidly, in contrast to a rifle bullet, which retains a focused, high-energy, single-projectile impact over much greater distances.
6. When a shotgun fires a slug (a single large projectile) rather than pellets, the wound produced can resemble that of a high-velocity center-fire rifle bullet, since a smooth bore can still fire a single projectile - it simply is not spin-stabilized by rifling (some slugs have external fins/rifling grooves cast onto the projectile itself to compensate).

Key medico-legal significance of the distinction

• Rifle/pistol wounds from rifled weapons show a single, well-defined entry wound with an inverted margin and abrasion collar, and the recovered bullet may carry striated rifling marks useful for firearm identification.
• Shotgun wounds vary characteristically with range: at close range they resemble a single large, ragged wound (pellets acting as one mass, plus wad and unburnt powder marks); as range increases, satellite pellet holes appear around a central wound, and the spread of pellet dispersion is itself used to estimate firing distance.