Gun Test
Ballistics: The science of the motion of projectiles, particularly firearms, including their trajectory, velocity, and behavior upon impact.
Barrel: The long metal tube through which a projectile is fired from a firearm.
Bore: The interior of the barrel; the diameter of the bore determines the caliber of the firearm.
Breechblock/Breechface: The part of a firearm that closes the breech (the rear part of the barrel where ammunition is loaded) and contains the firing mechanism. The breechface is the rear surface of the breechblock.
Breechblock/Breechface Markings: Marks left on the cartridge case by the breechblock, often useful in identifying the type of firearm or even individual weapon used in a shooting.
Bullet/Projectile: The projectile fired from a firearm, typically made of metal and designed to be expelled from the barrel.
Caliber: The diameter of the barrel or the projectile, typically measured in either millimeters or inches.
Cartridge: A complete round of ammunition, including the bullet, casing, primer, and propellant.
Cartridge Case/Shell: The container that holds all components of the cartridge (bullet, primer, propellant).
Comparison Microscope: A type of microscope used to compare two items side by side, often used in forensic ballistics to compare bullet striations.
Firing Pin (Primer Dent): The part of a firearm's firing mechanism that strikes the primer of the cartridge, causing the propellant to ignite. The primer dent is the impression left on the primer.
Gauge: A measure of the bore size in shotguns, indicating the number of lead balls of a given diameter that would fit into the bore. The lower the gauge, the larger the bore.
Greiss Test: A chemical test used to detect the presence of gunshot residue on a target, typically skin or clothing.
Grooves: The spiral cuts inside the barrel of rifled firearms that impart spin to the projectile, stabilizing its flight.
Gunshot Residue (GSR): Microscopic particles left on a shooter or nearby individuals after a firearm is discharged, containing elements like lead, barium, and antimony.
Lands: The raised areas inside the barrel of a rifled firearm, which grip the projectile and give it a spin as it travels down the barrel.
Magazine/Clip: A device that holds and feeds ammunition into the chamber of a firearm. "Magazine" is the correct term for a detachable or fixed feeding device; "clip" is often used informally but refers to a different type of mechanism.
Primer: A small explosive charge that ignites the propellant when struck by the firing pin.
Projectile: The object (such as a bullet or shot) that is fired from a firearm.
Propellant: The chemical substance (usually gunpowder) inside a cartridge that burns to create gas, propelling the projectile.
Rifling: The pattern of grooves and lands inside the barrel of a firearm that imparts spin to the projectile for stability during flight.
Rim: The edge at the base of a cartridge that helps in extracting the cartridge from the chamber after firing.
Shooting Tank: A device used in ballistics testing to simulate a real-life shooting situation, often with a
target that can capture projectiles for examination.
Shot: Small pellets fired from a shotgun, or the discharge itself.
Slug: A solid projectile fired from a shotgun, typically larger and more accurate than shot.
Striations: Small, microscopic marks on a bullet caused by contact with the barrel’s rifling, unique to each firearm and used for identification.
Trajectories: The paths that projectiles follow after being fired, affected by factors such as velocity, gravity, and air resistance.
Components of Gunpowder: potassium nitrate (oxidizer), charcoal (fuel), and sulfur (fuel).
How a gun shoots: When ignited by the firing pin, the chemical reaction between the components produces a large volume of gas, creating pressure that pushes the projectile (bullet) out of the barrel at high speed.
Pistols: Semi-automatic or single-shot handguns, with a fixed barrel and chamber
Revolvers: Handguns with a rotating cylinder that holds multiple cartridges. They must be manually cocked or can fire when the trigger is pulled.
Rifles: Long-barrel firearms with rifling inside the barrel to spin the projectile for accuracy. They are used for hunting or precision shooting.
Shotguns: Firearms designed to shoot a spread of pellets (shot) or a single projectile (slug). They are used for hunting birds or close-range targets.
Class characteristics: Caliber, firing pin impressions, breechblock markings, rifling patterns, and primer type that can suggest the type of firearm used but not the specific gun.
Rifling (lands and grooves): Unique pattern of grooves inside a barrel.
Firing pin impression: Mark left on the primer when struck by the firing pin.
Breechblock markings: Impressions left by the firearm’s breech.
Striations: Unique microscopic marks on bullets caused by barrel imperfections.
Comparison microscope: Allows side-by-side examination of two objects (bullets or cartridge cases) to look for similarities in striations, firing pin marks, or other characteristics.
Shooting tank: A device used to safely fire a weapon in a controlled environment, often used for test-firing ammunition to capture and compare the resulting projectiles and cartridge cases.
Bullets: Solid projectiles, typically used in rifles and handguns.
Shot: Small pellets, usually from a shotgun, that spread out upon firing.
Caliber: The diameter of the bullet or the barrel’s bore, typically measured in millimeters or inches (e.g., .22 caliber or 9mm).
Gauge: Used for shotguns, it refers to the number of lead balls of a given diameter that fit the barrel (e.g., 12-gauge is common). The higher the gauge number, the smaller the bore.
IBIS: A database used to store digital images of cartridge cases and bullets, allowing forensic experts to compare markings and identify firearms.
NIBIN: A U.S. national database that connects IBIS and other systems, helping law enforcement track ballistic evidence across cases and regions.
Determining how far a weapon was fired from a target: Measuring the distribution of gunpowder particles and other discharge residues around a bullet hole
Greiss Test: A test conducted on and around bullet holes to pick up Nitrate residue, turns pink.
How to convert mm to inches: divide by 25.4