These guns are mirco paper models, named "Little Zerstorung" and based on the game Gods of Steam, World War Weird, Weird Wars. This paper model was designed by Dragonz. The size is ca. 28~30mm. These were secret autonomous mobile guns that was developed by the hand of Moriarty.
You can download these weapon paper models from here: The Little Zerstorung Mobile Guns Mirco Paper Model Download