10.2 Characteristics and Firing Mechanism of Firearms

The mechanism's cycle (the exam's sequence): the cartridge's loading → the trigger's pull → the firing pin's strike → the primer's ignition → the propellant's burn → the bullet's propulsion (the pressure) → the spin's-and-flight (the rifling's grip) → the extraction-ejection (the case's ejection — the scene's evidence). The firearm's individuality: the rifling's manufacturing marks (the lands- and-grooves's number, twist-and-width — the class) + the bore's-and-breaching's irregularities (the wear-and-use's marks — the individual) — the fired bullet's signature.