Hotchkiss Universal: The Most Folding Gun Made
16m
The Hotchkiss Universal was a closed-bolt submachine gun submitted to French military trials in the late 1940s to replace the MAS-38. The French were looking for a compact SMG in 9mm Parabellum, and tested guns form the state arsenals as well as the Hotchkiss and Gevelot companies. The Universal (also designated the Model 010 by Hotchkiss) really doubled down on the compact elements, with a design that incorporated a folding stock, grip, magazine well, and telescoping barrel. It could fold up in to a remarkably compact package, complete with a loaded magazine in a completely safe stowed format.
A total of about 7,000 Universals were made, in what appear to be two series. The first were marked CMH (Carabine Miltrailleuse Hotchkiss) and serialized on the trigger assembly and the second marked CMH2 and serialized on small plates riveted to the stock tubes. Several variations on parts can be founds, including simplified front sight blocks and simplified rear sights - I suspect the simplified patterns were the CMH2 as an attempt to reduce the cost of the guns. Small batches were sold to Venezuela and Morocco, as well as an unidentified middle eastern nation and a few even to the French CRS security service. A small number were also tested by the Foreign Legion in Indochina in 1954.
Ultimately, of course, the MAT-49 won the military trials. The Universal was rejected for being too expensive and too complicated - both totally valid assessments. It is a gun that put all its chip on compactness, and made way too many tradeoffs in the process to be really viable.