Around 1946 Czechoslovak Army issued request for SMG prototypes that would be compact, cheap to manufacture using domestic resources, have decent capacity and also "have minimal center of gravity shift with emptying of magazine". Final winner was the Sa23 AKA "the bikepump", but some of the prototypes were endearingly wacky. This is my favorite, it has a double-stack magazine in the comb of the stock, bullets pointing upwards, and is mechanically more or less a fullauto Spencer carbine. It failed spectacularly, but would look great in an Iron Harvest setting.