The shotgun is a cheap model which has been bought from a pawnshop and it is being filled with birdshot. When a gun is shot with the end of barrel dipped in water will result in the explosion of the barrel. Birdshot is filled with about three-quarters of the barrel and the shotgun is setup in such a way that the string attached to the trigger allows the gun to be shot from a safe distance. A monitor has been placed close to the barrel to indicate any birdshot going out through the barrel. The trigger is pulled and a nasty explosion occurs which destroys the bricks the shotgun was placed on. Even though the gun explodes into two, no birdshot has escaped through the barrel.