Firearm Showcase: The Heckler & Koch SMG (I), 1980s Would-Be Successor to the MP5 – HIGH RES PICS!

In May of this year, I got the rare opportunity to travel to Heckler & Koch’s headquarters in Ashburn, VA, to take a look at some of the experimental and prototype firearms they have located there in their famous “Grey Room”. It wouldn’t be worth as much for me to just tell you about it and to snap a few foggy cell phone pictures, though, so I brought along Othais of C&Rsenal to help me take high resolution light box photos of these unique and rare firearms.


I mean, don’t get me wrong, I also took a bunch of crappy cell phone pics.


The first such weapon we’ll be taking a look at is simply called the SMG, although it is often referred to as the “SMG I” to distinguish it from the SMG II, which we’ll cover in a future post, along with several other firearms. As I mentioned in a previous post regarding a transverse drum magazine designed for the SMG I, the publicly available information on the SMG I amounts to an article by Jim Schatz published through Small Arms Review. Scant few images have been released of the weapon, too, which is why I am happy to publish for the first time the high-resolution photos embedded below! Enjoy!

SMGImodified3 SMGImodified SMGImodified1 SMGImodified2 SMGImodified4

If you want to download all of these photos in their full resolution, you can follow this MediaFire link to a zip file containing them.

Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • MacK

    yay… a UMP 9, oh wait… UMP9 (ii)? durr hurr HK. :rolls eyes

  • BattleshipGrey

    That thing’s pretty sweet, curses upon all gun laws and HK pricing that prevent me from owning it (had it been released).

  • Anonymoose

    Mounting a muzzle device looks awkward, the Thompson/Uzi/MAC-10-style charging handle looks out of place on such a fancy futuristic weapon, and they seem to be getting way ahead of themselves with that HK21 1000m rear sight.

    • The barrel has external threads shrouded inside the receiver. Open up the photos, and you can see them through the vent closest to the ejection port.

    • randomswede

      I could be joining together memories here but; as I recall the SMG II project had the “too many cooks” problem as well as trying to be perfect in every regard as well as better than the MP5 in every way.

      • It looks kind of like that is the case. SMG I is the slicker gun, IMO.

    • FWIW: The SMG I’s rear sight was only adjustable from 25 to 150 meters, in 25 meter increments. It could also be set for the use of either supersonic or subsonic ammunition.

  • Major Tom

    What is it with gun makers and making tons of sharp edges and flat angles these days? Did the fishgun XM8 really turn people off to the concept of curvy ergonomic furniture?

    • BattleshipGrey

      IMO yes, the XM8 was a great example of what not to do.

      • Mechanically, it wasvery sound.

        • Major Tom

          But its main flaws were:

          – Its barrel melted.
          – All of its furniture was proprietary H&K suckage.
          – Its barrel melted.
          – All of the compatible optics and mounts were proprietary meaning the Army couldn’t use its M68s or ACOG’s.
          – Its barrel melted.
          – H&K was naturally price gouging so the cost of it was exorbitant relative to an M4A1.
          – Its barrel melted.
          – Its modularity features such as being able to convert to a carbine or LMG or DMR or PDW with just a few tools and parts was extremely underwhelming.
          – And did I mention its barrel melted?

          • The barrel melted? Yeesh– I’d only heard of the barrel getting way hotter way quicker than it should have and melting all the plastic furniture everything else.

          • Yeah, “its barrel melted”? I don’t think you know what you’re talking about.

          • Alex Sweers

            Where are your sources the XM8 barrel melted? I have a fairly extensive (and probably unhealthy) knowledge of the XM8 and never heard of issues with the barrel melting. In reality, it was an excellent assault rifle but was doomed due to politics. Stop spreading unfounded BS on a weapon you probably have a limited understanding on.

          • One of my current in-depth research projects is regarding the XM8, and while I think the rifle probably wouldn’t have been as good as the M4A1, “barrel melting” is a problem I’ve never heard of before.

          • M

            It’s not physically possible for a barrel to melt from shooting 5.56. This was discussed on TFB a while back. The barrel would burst and the weapon be inoperable before it would melt.

            I think you mean the handguard melted

        • BattleshipGrey

          I don’t doubt that. I just meant esthetically.

    • FWIW: This was designed back in the early 1980s.

      • ostiariusalpha

        Right, “these days” for the SMG I was 1981, a good bit before the XM8 was a twinkle in its designer’s eye. Sharp edges and flat angles were the fashion back then.

        • Just look at the HK G11.

        • Giolli Joker

          And they look more “weapon” and less “fish”…

      • randomswede

        It’s a little sad that you’d have to post that, the article has no year in it but the SMG II isn’t really a secret.

      • Giolli Joker

        “this example was manufactured in November 1983”

        Like myself.
        Now I’m in love.

    • EnderHuman

      Isn’t the ARX160 a fishgun too?

  • thedonn007

    Needs more picatinny / MLOK / KeyMod.

    • ostiariusalpha

      The air vents might as well be M-Lok, their shape is perfect.

    • JSmath

      Well before the thing’s time. It does seem to have a proprietary optic rail piece on top, though, which would be nice.

      • Nah, I’m pretty sure adjustable warehouse storage racks have been around since the ’70s.

  • Sam

    Telescoping stocks are cool and awesome for compactilization (that’s a word for today), but I pretty much had shooting with them. Or an AK underfolder. Cheek weld? Not even once.

    • randomswede

      Someone correct me if I’m wrong but; isn’t the AK underfolder used with chin weld?

      • wetcorps

        Cheekweld at all costs seems to be more of an American thing.

  • Rnasser Rnasser

    That foregrip is too slanted…

  • d_grey

    Definetly more sexy than the UMP.

    • Stan Darsh

      All HK needs to do is swap out the direct blowback for the MP5’s roller delayed action and it would be damn near perfect.

      • d_grey

        That would be revolutionary, it’s a tried and tested system and better than most systems in use today.

  • Giolli Joker

    Does it have roller guts or is it a simple blowback?

    • The SMG I, SMG II, and MP2000 were reportedly all straight blowback.

      • Giolli Joker

        That’s sad…

        • Gary Kirk

          Why none ever achieved beating the champ.. MP-5

  • Monty01

    This weapon makes me think that a 9 mm version of the MP7 would be a compact and effective weapon – definitely be a replacement for both MP5 and UMP. The MP5 was always a good gun, but somehow the UMP never replaced it. Many people are convinced that the negative stories about the G36 have killed polymer in military / LE weapons, but this prototype and the MP7 show it can still work very well.

    • No, SMG I and II both predate the UMP.

    • A 9mm MP7 would be too big, too awkward, too fiddly, and waaayyy too expensive for what it is.

      …I mean, the MP7 already is all of those things, it just has the added novelty of firing a moon caliber.

  • John

    Heckler and Koch REALLY don’t like rail systems, huh?

    • Well, this firearm predates the picatinny rail by many years and their crystal ball broke in the 1970s.

      • Gary Kirk

        Actually the picatinny rail design was started by A.R.M.S. in the early 80s, and another company was working on it as well.. Didn’t receive the Mil-STD-1913 from picatinny arsenal until testing was completed in the mid 90s though..

        • Sure… But this gun still predates even A.R.M.S.’ working prototypes that would become 1913 rails.

          • Gary Kirk


  • Was this in HL2?

    • forrest1985

      Not exactly, it was meant to be, but was cut from final game in favour of MP7.

      • There we go. It had that “in the same vein” feeling.

  • Mc Cain

    Wow….it sure looks like it would easy to blow a hole through a hand or finger with the foregrip literally right on top of the muzzle.

  • Jeremy

    This is the gun we will use to board enemy spaceships.

    • Canonically, I’m pretty sure that’s a P90.

      • Reef Blastbody

        Yes, the SG teams assigned to capture Hatak class capital ships carried FN P90s. 😀

  • FactChecker90803

    The successor to the MP5 already exists, it’s the SIG MPX.

    • Green Hell

      Eh… nope. It’s overdesigned, flawed in more ways than one and have “US civilian market” written all over it.

      • Evan Ferguson

        Care to expand on those claims? The MP5 is far from perfect.

  • Sianmink

    Elements of the later UMP are apparent, as is that it was designed before M1913 rails were a thing.

  • TheNotoriousIUD
  • aka_mythos

    I’m sure we’ll see this in a good many movies.

  • Were there any performance enhancements in mind with this design, or was it primarily intended to be a lower cost version of the MP5?

    • ostiariusalpha

      Not just lower cost. The SMG I was designed to switch quickly between suppressed subsonic ammo and unsuppressed supersonic ammo, and the simplified blowback operation supposedly was able to handle a wider assortment of cartridge loads than the MP5. It also was smaller and lighter than the MP5, with fewer snag points for clothes and equipment to catch on. If it had panned out, and the unit price stayed low enough, there were preliminary plans to issue it as a PDW for the rear echelons in addition to front line use.

  • germanlion

    They should produce this gun (change the foregrip though).

  • Evan Ferguson

    The mp5’s roller delayed action has issues with heavy for caliber loads, is prone to firing when dropped, has limited attachment options, bad trigger, no last round hold open, heavy, and I’ve seen an mp5sd choke consistently for no apparent reason and was not able to be put back into service in the field. Despite it’s mythical video game and movie status, and the fact that it is actually a pretty good shooter, it’s not perfect. Nothing is, for that matter.

  • Sid

    Ooo a unique pre-may I wouldn’t mind getting into my collection..

  • mechamaster

    Seriously, HK should revive this concept again…

    1st. Starting with the ‘drop-in’ MP5 upper in blowback mechanism like the SMG concept…

    2nd. Added the multi caliber conversion kit. ( maybe in PDW high velocity cartridge like the .22TCM9R / 6,5 CBJ )

    3rd. Profits ??