Despite its tendency to jam, the Sten Gun's simplicity allows it to operate in harsh conditions with very few probabilities of breakage. And even if one did break, spare parts are more than plentiful.
Named after the verb and not the place (though they wouldn't be out of place there), sewer guns are cheap, scrap-metal SMGs typically taking after the Sten Gun, which were it not for British industrial standards, would probably be considered a generic scrapgun. They are typically chambered in 9x19mm Parabellum, Oceanyka's most common automatic pistol cartridge.