Firearm Showcase: The Heckler & Koch SMG II, 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.

Today we’ll be looking at H&K’s follow-on design for the SMG I (which didn’t receive that name until today’s weapon was produced, originally it was just the “HK SMG”). If you’re thinking “didn’t we already do this one?”, that’s because the SMG II looks extremely similar to its predecessor. You can compare the two in the image below:


Top: SMG I; bottom: SMG II.


The SMG II is an improved version of the original SMG, with several added features. Instead of using an MP5 magazine, the SMG II uses a new pattern of polymer magazine. The HK21-type sight was replaced with a more classic HK drum sight, and the butt of the stock became a new, smaller sheet metal piece. Perhaps the most significant feature was the pressure selector, located at the front of the magazine. This allowed the SMG II to reliably operate with either high pressure NATO service ammunition or low pressure subsonic ammunition, similar to a regulator setting on a gas operated gun.

DSC_0899mod DSC_0897mod DSC_0903mod DSC_0902mod DSC_0901mod DSC_0900mod

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


  • Gambler X

    The only time Id ever seen this before TFB was strapped to a London policeman after the Underground bombings, then never again like I’d imagined it.
    “But it looks like a Spectre and a MP5 had a baby!” which was the only way to describe it.

    • Burst

      They’re in USE?

      I thought this was a prototype that was never shipped.

      • Gambler X

        did I say any of that?

        No, Im just telling you where I saw it.

        • Tom

          Hate to call you out but as far as I am aware the SMG II never made it into any use, what you saw was most likely a common-a-garden MP5K with the sliding stock.

          • Gambler X

            I know what an MP5 looks like, I own one. Thanks for playing.

        • They’ve got semi-auto MP5s, is my understanding.

          • Gambler X

            during the whole incident id seen stuff Id not seen before or ever expected with Metro, the UMP in 9mm with the curved box magazine, and the one im referring to. It could have been the MP2000 but it had that raked fixed grip, same as the SMG 1&2.

            Im just saying until the first TFB article id never seen that gun outside of that picture.

    • BS

      No chance. Most probably you have seen the UMP

      • Gambler X

        I know what a UMP is and what it looks like, Ive even shot one. Try again

    • Mark

      I worked for HK for little bit at the Sterling facility in VA and rep’d for them for years when they used the Evans Group. Although I did not deal with the technical/engineering side the HK SMG I/II and the MP2000 were never fielded by any military/police force or any other combat group. Only the HK SMG II was ever even tested by anyone and it failed in favor of the MP5. The SMG I, MP2000, and the MP5-PIP were never tested by anyone other than the gunsmiths that designed them.

      • Burst

        What part of the testing did the SMG not hold up on?

        • Mark

          I don’t know, it was before my time there but I can ask a older friend of mine that was with the R&D up there. I did Law Enforcement sales and I remember seeing a few pictures of the HK54A1 which led me to ask someone about the SMG guns. Only about 20 SMG I s were made and 20 SMG IIs. There is a long standing rumor that some group did pick up the SMG II and ordered 60 but from asking around that was BS. The HK54A1 was tested by defense personnel and supposedly was viewed favorably. It still ranks as one of the quietest suppressed sub guns ever built. I know they had trouble with the complexity of it though which led to the development of the SMG series. I’m guessing it was a combination of money and performance problems that all new guns have that eventually get ironed out but like I said I never saw or read anything from the tests. The MP2000 was ordered for testing by the Navy. They ordered 10 but the order was never fulfilled.

          • Burst

            I can’t upvote due to my greyface, but thanks for sharing.

        • Mark

          I will say this though. I know they made about 20 of both the SMG I and SMG II. I have no idea where those are. Like many prototypes there is a good chance that someone somewhere who knew somebody at HK high up has it in their private collection.

  • TheNotoriousIUD


  • Paul Epstein

    I’m very curious as to what the pressure selector actually does- the first guess that comes to mind is that it disengages the rollers and turns the system into pure blowback. But I’m not positive that the SMG 2 is even a roller locked gun, despite it’s similarities to the MP5. And if it’s already pure blowback in both modes, that doesn’t leave an obvious answer. Disengage a recoil spring?

    • Brocus

      by pressure selector you mean the two ‘buttons’ above the trigger guard? lower is mag release, upper is bolt lock.

      • He means the “High-Low” lever that is described in the article, which is in front of the mag well.

    • ostiariusalpha

      There were no rollers in either the SMG or SMG II.

    • Mark

      When turned to Low it diverts a small amount of gas through a port into a small chamber under the barrel that allowed standard supersonic bullets to be brought down to subsonic. I saw these guns a long time ago and never even noticed the lever. Pretty interesting.

      This is from an article on the gun from Small Arms Review.

      “Located on the receiver just forward of the flared magazine well this lever had two positions, “L” for low and “H” for high. Pulling out the front captured locking pin and sliding the plastic vertical foregrip forward off of the receiver revealed a small gas cylinder mounted parallel with and under the barrel that resembles the CO2 cartridges commonly used in airguns. When the gas relief valve was set in the “L” position a port opened in the barrel that allowed a measured amount of propellant gases to escape into this “holding tank”. By diverting this gas away from behind the projectile in the bore the exit velocity of the projectile is effectively lowered. A supersonic ball round fired in the SMG II with the gas port open departed the weapon below the speed of sound and thus eliminated the telltale “crack” of a supersonic projectile. Once the projectile left the bore in route to the target the gas remaining within the cylinder exits from the muzzle”

  • Nicks87

    Look at how crazy thin the weapon is, perfect for concealed carry… But just for executive protection of course 😉

    • TheNotoriousIUD

      Or a trip to the hardware store.

  • DIR911911 .

    good looking gun , but that forward grip gives the impression that it’s angled back a bit , looks like it could possibly bang your hand in a magazine swap. but very nice.

  • Joey JoJo Jr.

    Great pictures! Probably the clearest I’ve seen of the SMG/ SMG II series.

  • De Facto

    It certainly looks snazzy. So why didn’t this wind up replacing the MP5?

    • Burst

      Because the MP5 was already better than everything else out there, and the ones in use weren’t exactly falling apart at the seams.

      A case of too much, too soon.

  • PK

    “If you want to download all of these photos in their full resolution”

    “If”? Oh, no, no one would have any interest in those whatsoever…

    Truly, thank you both for doing this, I wondered if there would be proper resolution files available at some point.

    I don’t suppose there are any plans to release the full, uncompressed files in the future? As wonderful as these are, there are artifacts when enlarged past 1:1.

    • I’ll whip up a few Imgur albums later today.

      • PK

        While I genuinely appreciate the thought, imgur will further compress the files and introduce more artifacts. What I’m mainly curious about is if there are entirely raw files straight from the camera (feel free to strip EXIF data of course)

  • Erik B

    It resembles very much to my B&T APC9 with their latest stock.

    Thanks for that.

  • Joe

    I wonder if it would outperform the UMP?

  • Jim N Jenna SK


  • Vitor Roma

    Roller delayed?

    • ostiariusalpha

      No, just blowback. The internals aren’t as cool as the exterior.

  • ArjunaKunti

    Wonderful pics!

    In case of adoption the HK36 with 4.6×36 in the 70’s, the final design would look like this SMG.

  • Timmybadshoes

    I am a huge fan of she’s and anything pdw. Shame this was not brought to fruition but then again it would be one more HK firearm for me to lust over but never be able to have.

  • Sasquatch
  • To Tin Fung

    this. this is the reason why i love TFB so so much.

  • Jonathan Ferguson

    Sorry, but I do this for a living, not a hobby, & if an HK SMG prototype was carried in anger that’s big news. Any chance you could re-find the photo?

  • AirborneSoldier

    3 round burst added to selector switch