Firearms and Ballistics Exam with Correct Answers

Firearms Identification - discipline mainly concerned with determining whether a bullet or cartridge was fired from a particular weapon Rifling - the spiral grooves that are formed in the bore of a firearm barrel, makes projectile spin when fired Grooves - the flat part of a barrel Lands - the raised part of the barrel Brooch cutter - used to create rifling impressions in a barrel Caliber - the diameter between the lands in mm -.22 caliber = 9mm - 45 caliber has .45 in diameter Caliber is calculated by - measuring the distance from land to land in hundredths of an inch or mm Events that occur when a firearm is discharged and a projectile is fired are - 1. A round is loaded and locked into the breech, the round contains a cartridge case, a bullet, a propellant, and a percussion cap 2. The firing pin is mechanically restrained and compressed when the firearm is cocked 3. As the trigger is pulled, the hammer mounted firing pin is pushed forward to strike a small hole in the breech face, hitting the primer cup. 4. The primer contains a mixture of sensitive chemicals which rapidly burn, producing hot gases that ignite the propellant 5. As the gunpowder is ignited, the gas expands which eventually forces the bullet down the barrel of the firearm The rifling techniques that give a bullet class characteristics are - -number of lands and grooves -Width of lands and grooves -Depth of lands and grooves -Pitch -Twist The individual characteristics of a bullet are - the machine markings, or striations all along the lands and grooves -These are created when the barrel is rifled, no two barrels have the same markings -These markings leave unique impressions on a bullet which allows it to be traced back to a specific firearm Cartridge case class characteristics - -manufacturer -shape -caliber -composition