Armstrong had transfigured broken pieces of glass into lead pellets, had conjured an invisible rifle, had put a Silencing Charm on his conjured rifle, then he kept using an overpowered Banishing Charm to move the lead pellets through the rifled barrel and out. The Banishing Charm was intended to stop when the lead pellet had moved to an inch from the end of the barrel. The disadvantage of the setup: it was not deadly beyond a hundred-yard range. The advantage: no muzzle flash and no spell flash; so to the victims, the lead pellets came seemingly out of nowhere.