The Railgun (TBD) (レールガン（仮）) was a weapon looking like a railgun and capable of storing gigantic amounts of magical power before firing them in a destructive blast.[1]
Overview[]
The railgun as a clothing rack
Developed by the Doctor, who didn't even bother to name it properly, as a means of countering the Mage-Killer soon after he created the Crimson Demons, it impressed the red-eyed chuunibyous with its power, despite the rare parts it was composed of unable to withstand the backlash of every shot. At some point in time, it was used to take out the Mage-Killer when the anti-magic weapon went berserk. However, over time its instruction manual became unreadable even to the Crimson Demons, so it was later used as an unrusting legendary pole for hanging laundry in Chekera's clothing store at the Crimson Demon Village.
When Sylvia gained the Mage-Killer and used it to attack the village many centuries later, Kazuma according to the notes left by the Head Researcher realised the Railgun's ability to overcome even the magic-nullifying effects of the Mage-Killer. He proceeded to set its sights on Sylvia while getting it charged with magic power from Aqua and Megumin, though the killing shot ended up fired by Komekko before the Railgun melted down from the strain.