RIA: Japanese Trials Gas-Operated Pedersen Rifle

The Japanese semiauto rifle trials of the early 1930s had a total of four entrants – Kijiro Nambu and his company, Tokyo Gas & Electric, the Tokyo Army Arsenal, and Nippon Special Steel. This rifle is one of the third iteration of the design from Nippon Special Steel. It is a design based originally on the Pedersen, but with substantial changes. It is a toggle-locked and gas-operated action with a gas piston that moves forward upon firing. It feeds from a ten-round detachable box magazine, which is unfortunately missing on this example.

In total, 13 of these rifles were made for trials, with 4 of them actually being tested (and firing over 100,000 rounds between them without any extraction problems, apparently). This rifle did have some accuracy problems, though, which would be fixed by its designer for the fourth and final trials, at which point it and the Tokyo Army Arsenal rifle were determined to be of equal quality – and then the whole program was dropped as the Marco Polo Bridge incident caused the Sino-Japanese War to quickly intensify.


  1. I honestly reckon it’s got a kinda utilitarian beauty. It looks pretty functional and well thought out (I get weirdly happy when I see captive pins being used in disassembly) and with the steel and wood contrast I really can’t find it ugly.
    What I find interesting is the Japanese clearly had a few very decent self-loading rifle designs available to them, but when they realized there was a pressing need towards the end of the war they decided to reverse engineer the Garand instead. Seems a lot more finicky an idea.

    • “decided to reverse engineer the Garand instead”
      I suspect that it was because it was Navy (IJN) not Army (IJA) project, they might simply don’t know about that design or don’t want bother with it.

      • More likely the latter reason. It would hardly be surprising given — to put it mildly — the acrimonious, long-standing rivalry between the two services, complicated by the even more deadly, fractious and self-destructive rivalry between the Strike North and Strike South factions within both organizations, and made even more Machiavellian with the constant meddling emanating from the Emperor’s Cabinet and perhaps the Emperor himself, along with undue internal influence ( exacerbated by cultural tenets, i.e., the exceedingly close relationships between business and Government ) exerted by principals within the Japanese military-industrial complex of the time.

        Bear in mind that I am referring to the factors that steered the course of Japanese weapons acquisition as a whole, but I would not be in the least surprised if one or more such factors played a part in the demise of an otherwise potentially promising small arms program.

  2. Fascinating.

    But if the gas system pulls the op-rod forward to unlock the bolt and so on, doesn’t that make it a variant or version of Sørensen Bang’s gas-system? Sort of a John Pedersen toggle-lock meets Bang’s rifle design?

  3. Going back to Denny’s comment on the Japanese copy of a Garand, It’s often easier to start with a clean sheet of part than it is to reverse engineer and de-bug an existing design (a concept that applies equally to the state sector – and as a part of that, military procurement)

    That said, a toggle lock has considerable merits in a gun. Note the success of toggle locks in many of the lever action rifle designs and in the Maxim and Vickers MGs.

    A toggle can be arranged to provide very large mechanical advantages for extraction (think of the toggle arrangement in a re-loading press, or the toggle presses used for deep drawing metal cartridge cases), followed by lower mechanical advantage for faster movement for the remainder of the cycle.

    A toggle is also potentially more resistant to dirt, and lower in friction than a sliding bolt, so long as the pivot pins are smooth and remain sort of lubricated.

    The gas piston rod in tension is a stroke of genius (Bang and Hatcher; eat your hearts out!).

    I think it was Sullivan (AR18 designer) who would later use ball joints to allow a thin gas piston rod to be used in compression, without it cocking the gas piston over to one side and inducing un necessary friction and wear.

    One of JM Browning’s last patents was for a toggle arrangement. I’ll see if I can find the number.

  4. Wait a minute!! I think this might be the Japanese Pederson I saw in a manga, only that the front sight was closer to the muzzle, a curved-bottom magazine was in place, and a scope was fitted!

    • Master Cherndog:
      With my background, plus being much closer to the descriptive adjective “blind as a bat” than most, my first reaction was how one might mount a scope on this thing without it looking like a giraffe on stilts. That toggle is quite high for that, but I would still like to have one even if I had to make a replacement magazine for it. I would like to see this one shoot even if single shot.

      • Try using the typical offset scope configuration used on the Type 97 sniper rifle. The scope does not therefore need to be above the toggle action. With that in mind, it stands to reason that once the fixed power lenses are zeroed for the rifle (Japanese practice mentioned last year), toggle flip won’t be a factor in clearance since the optics are not directly above the receiver. The rifle will not take two minutes or more to get a full magazine, having retained clip-loading capability due to said offset scope.

  5. Another excellent presentation and a beautiful, functional, historic firearm.
    Too bad no magazine!
    Got a couple of comments– just another angle, mis dos pesos.
    History: Regarding the Marco Polo Bridge “incident,” many historians (including myself) pinpoint that incident as the opening battle that became WWII. Hitler and Mussolini where come late-lies although the Italians were invading north Africa during the 1930s.
    Also, mechanically, at the bottom muzzle area gas port position is the Chinese word (cong-gi in Japanese); the character means small. Maybe the lever was positioned on that until the gun got a bit dirty and then was switched up a notch where possible that port(hole)was larger?

  6. The first thing I thought of when seeing a gas piston rod pulling rather than pushing was there’s no surprise there; most Japanese hand saws have the handle on the other end so it cuts on the pull rather than the push, so there’s no flexing of the blade when one makes a cut.

  7. Clever mechanism although little too complex yet. Still quite a jump over Pedersen’s design. I like the rugged appearance (which is not exactly so much present in gas-block area).

  8. Looking again at this pull-type operation….. that means the mass inertia of rod did not add to opening of action. It merely tipped the lock out of balance. Therefore, unless I am wrong, it was the remnant of gas pressure in barrel which did the extraction and ejection.

    The system then may qualify as “gas delayed blow-back”.

    • I’m guessing that there should be plenty of momentum in that toggle.

      although that can be used both ways,

      as it provides significant resistance if there is still significant residual pressure in the chamber

      and, a considerable mechanical advantage for pulling teeth extracting sticky cases during the powered phase of gas piston movement

      I’m going to watch again to get a better look at what look like built in mag feed lips.

      It would be really interesting to see the all straight line and on bore axis version in the next iteration.

      • Well, assuming the centre joint is below connecting line of 1st and 3rd joints then, by sudden lift produced by mentioned rod may produce some momentum. Sort of “knee-jerk”. 🙂

        Still, you know, I wonder why the guy did not go straight ahead at it just like anybody else would – with KISS approach, without narrowing field of operability. I’d presume, since he was a doctor, he enjoyed the unusual ways of doing things. I kind of feel the way he was.

        • The gun is probably locked with the center joint low as you described. The camming hooks seem rather long which the operating rod would tip up, bypassing a significant amount of the mechanical disadvantage provided by the toggle action. This shouldn’t matter much with a locked system, and may even be helpful. As the knee rises and moves rearward, it pulls the bolt to the rear imparting some momentum to the bolt. I assume the rear projections on the rear toggle link are what forces the op-rod forward when the toggle is manually cycled.

          • That’s my understanding. It looks kind of marginal considering fouling, ingress of dirt, wear influence ad so on. This is what I meant under term “zone of operability”.

            As someone suggested, it would be nice to have couple shots fired scanned by video.

          • Perhaps the new owner will be kind enough to let Ian film it with the slow motion camera.

    • Another possibility is that it is “gas powered” as a subset of gas operation. If you consider John Brownings early experiment with a muzzle mounted hinged flapper with a hole in it and a tension rod to operate the lever on a lever action rifle, that didn’t use either momentum transfer or residual chamber pressure for operation. It was muzzle gas powered. It is possible that reliability could be enhanced using such a system.

  9. “The Japanese semiauto rifle trials of the early 1930s had a total of four entrants – Kijiro Nambu and his company, Tokyo Gas & Electric, the Tokyo Army Arsenal, and Nippon Special Steel.”
    When Japanese realized need for self-loading rifle? 1930s were first trials of self-loading rifle or were there earlier trials?

    • I’d think that first such notion may have come when they encountered Chinese with their Canadian made Brens and later Dutch with Johnsons. When they came to contact with US Marines equipped with Garands, it was little too late. Up to that point nobody really seriously thought about semi-automatics.

  10. I agree that this rifle is not ugly at all for a military rifle. Maybe I have spent too much time looking at French rifles, I don’t know.

    It is odd to think that if things had worked out a bit differently, Japan and the USA would both have fought with Pedersen type semi-auto rifles.

  11. Japanese saws…the handle is on the other of the other end. As I understand, Japanese woodworking was initially, (I have no dates), done on the ground. And in woodworking, the essential question is, “How you gonna hold it?” In the west we use and used vices and stops. The Japanese held things with their feet. Therefore, cutting, (and planing)was and is done on the pull stoke. But what I’m getting at is, as Ian said, tension. Japanese saws are very, very thin, and the comparison is to a blade of grass. Pushed in water it buckles; pulled in water, it stays straight.

  12. Issue multiple magazines and this would have been the best rifle of the war! Perhaps outdone by the FG 42.

    • Well, Kawamura’s design trumps the early FG-42 in terms of accuracy, mass balance, and snag resistance through underbrush. The FG-42, on the other hand, has better penetration through concealment and a cartridge which feeds better in automatic weapons…

  13. For what it’s worth, I noticed that on the gas block, the control’s bottom position is marked “less [gas].”

  14. If as good as it sounded just as well the Japanese didn’t adopt it. Probably saved countless thousands if not tens of thousands of lives.

  15. Looking for technical drawings on this one. Any ideas where?

    Ian already speculated they were lost to time, and I contacted the Japanese Embasssy. I also contacted a Nippon Steel company in Japan, but there’s no telling if they’re the same as the pre WWII company.

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