A shotgun is a type of firearm characterized by its mechanism for propelling a dispersed payload, typically consisting of numerous small projectiles known as shot, or a single, large projectile called a slug. The firing process utilizes a propellant charge, which, upon combustion, generates rapidly expanding gas that forces the payload down the barrel. The bore of many shotguns is smooth, meaning it does not feature the spiral grooves (rifling) necessary to stabilize a single, solid projectile. Instead, the initial velocity and angle of the dispersed shot are determined by the internal geometry of the barrel. The energy transfer and ballistic behavior of the payload are governed by principles of fluid dynamics and chemical propulsion, resulting in a pattern of spread that increases rapidly after exiting the muzzle.