Viper MkI: A Simplified Steampunk Sten

The Viper Mk I was an experimental submachine gun developed in the UK for use by military policemen in post-WW@ occupation West Germany. It was a simplified Sten gun (full-auto only, without the semiauto option normally included in the Sten trigger mechanism) put into a wooden housing. It was intended to be carried slung over one shouldered fired under the arm with just one hand. To this end, it had neither sights nor trigger guard. The whole concept seems pretty questionable, and while multiple different Viper submachine guns were designed to fill this role, none were ever adopted.

Many thanks to the Royal Armouries for allowing me to film and disassemble this very rare rifle! The NFC collection there – perhaps the best military small arms collection in Western Europe – is available by appointment to researchers, and you can browse the various Armouries collections online here.


    • This is the submachinegun equivalent of “Fitz Special”, and was no doubt meant for a security situation that never materialized. As a weapon for someone running a traffic control point, or a secured entrance to a facility, I can see why the Brits came up with this. Post-war Germany never got quite lawless enough, but if I were a British soldier on guard in Palestine? Yeah. I would want something specialized like this.

      • Yes. I’m thinking about the assassination of Count Folke Bernadotte and Col. André Sérot by four members of Lohamei Herut Israel/ LEHI in 1948… If a bodyguard? Yeah, I could see the appeal.

  1. If I would have to describe it shortly I would say: alternative ergonomics.
    It reminded me about Delacre Modèle 1936: which also was supposed to be one-hand sub-machine gun, but it actually would have sights. Does Viper Mk I count as bull-pup?

    “military policemen”
    I guess that someone might want to give ability to drive motorcycle with one hand and fire with another.

    How heavy is Viper Mk I (unloaded)?

  2. Thankyouthankyouthankyou! I’d long been interested in this crazy prototype. During the occupation, what with highly-indoctrinated fascist youths and the werwolf erstwhile “Auxiliary” stay-behinds, the idea was for the military occupation authorities to have an easy-to=port under the dominant arm SMG that would be ready at a moment’s notice, and swing from under the arm by a carry strap or rig. Obviously a point shooting weapon, which is problematic. I’d think this set up would be just the thing for people interested in police type armament in an age of deranged whackos and psychotics bent on mayhem, and for that matter, people interested in PDW designs.

    So glad I support the ongoing research on Patreon! Awesome stuff!

    • Given how even the British marksmanship manuals for the Stem emphasized firing from an “armpit assault” carry, this wouldn;t necessarily be any *less* accurate than a standard MkII or MkV Sten.

      Now, if you even pretend to use the sights, a standard Sten would be far more accurately (I tend to shoot them shotgun style — looking over, not through, the sights, focused on the target, and do pretty well.)

  3. Actually, the more I stare at it, the more I could see contriving a sling like that for an “off the shelf” P90 by FN in 5.7mm so it could be carried that way… With the added advantages of a rudimentary sight of course! Also, no magazine sticking out at an awkward angle (Bring on the Bergmann mp35 or Furrer MP43 you say?! Ha!)

    For that matter, there was that crazy GIAT French prototype PDW with no stock and two pistol grips that apparently had some sort of “tupper ware” holster it snapped into on the belt or thigh…

  4. A brilliant addition to public historical knowledge; on so many levels.
    Dave’s already suggested how the weird times that lead to the really weird thinking that resulted in the manufacture of this beyond weird gun.
    On top of that the film is a class in old woodworking skills that were once common, but are now just a hobby in too much of the rich parts of the world.
    Best of all though, for me, is the string that holds the sling on! Sisal was the gaffer/duct tape of the world. Never mind the steam engine, sisal and a hammer was what made things work until, pretty much, the 21st Century; and I can think of no other channel where it has a staring role, even if uncredited.

  5. If I recall correctly, the Annihilator, the Thompson submachine gun prototype, had neither sights nor buttstock and was full-auto only with a paper tape feeding mechanism. Designed for walking fire in trench warfare, the original concept is why the Thompson’s buttstock was so long compared to just about anything else.

    • Eh, I’d be inclined to agree… But these days what with “head up displays” and the FELIN “future soldier program” and electronics, I could see aiming a modern firearm this way and having it visible in a “head up display” or screen of some kind… It’s coming sometime soon I’d bet…

    • “One of the stupidest ideas ever.”
      I am not so sure about it. Certainly it was narrowly specialized, optimizing for quick deployment and close distance at expense of ability of aimed or single-shot fire.
      It might work in certain circumstances.
      Note for example that during Warsaw Uprising sub-machine gun unofficial name used by Polish forces was “rozpylacz” ([lead] sprayer). Read more: chapter STORY WRITTEN IN ENGLISH here:

  6. Looking at the wood stock, it’s screaming “I’m a test piece for a Bakelite part” Especially the raised checkering at the back, that are shaped like they’d been cut into a mold cavity with a ball-nose endmill.

  7. It was designed for motorcyclists, that’s why it was designed to be hip-fired with one hand (you can’t aim when you’re on a bike).

    The reason this piece is so crude is because it was a proof-of-concept proposal, hand-made by Derek Hutton-Williams (later director of RSAF Enfield). A more refined, purpose-built version with sights was developed and it was tested but didn’t meet the OB’s specifications and was rejected.

    • Oh, and I should also point out that the model seen in the video was actually designed in 1942, and was not intended for MPs in occupied Germany. That was a proposal for the later Mk.III, which only came around after the war had ended.

  8. If you arrested a Nazi all his mates would try and stop you, so you hold ones head and spray the rest then run off if back up doesn’t arrive; its not like ze Nazis weren’t popular.

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