Full auto crossbow by Jörg Sprave. Cranked by a drill and utilizes a rack-and-pinion firing mechanism.
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8:10 video:
https://www.youtube.com/watch?v=tbKGjRoSofA
Previously:
https://www.homemadetools.net/forum/...189#post126305
https://www.homemadetools.net/forum/...6956#post84708