Earlier this year police in Medina Minas Gerais received a call that a man was firing firearms on a public highway. Upon arriving at the scene police encountered a 52 year old man with a shotgun and after searching his house discovered four more homemade firearms. This quad barrel favela sweeper definitely takes pride of place.
A quick and dirty improvised firearm assembled using pipe fittings available at any hardware store. Ammunition in this case has been improvised using nail gun charges with the crimp removed and a lead projectile inserted. The weapon functions by pulling back the ball end of the spring loaded striker bar and releasing to fire.
An example of a criminally used improvised 12 gauge pipe shotgun. The front tube houses the barrel while the rear tube contains a spring and a striker which is pulled to the rear and released to fire. A bolt attached to the front of the rear piece allows the gun to be locked and unlocked in a bayonet type fashion for loading and unloading.