Thorpe EM-1: A Bullpup Take on the Roller Locked Gerat 06

Armament Research Services (ARES) is a specialist technical intelligence consultancy, offering expertise and analysis to a range of government and non-government entities in the arms and munitions field. For detailed photos of the guns in this video, don’t miss the ARES companion blog post!

The EM-1 was one of the British post-WWII rifle development projects with the ambitious goal of replacing both the infantry rifle and the submachine gun with a single select-fire weapon optimized for combat within 600 meters (as opposed to the prior doctrine of 1000m effective ranges). The design team was led by a man named Stanley Thorpe, and the first rifle was ready for test firing in December 1949.

Mechanically, the Thorpe EM1 used the same roller-locked operating system as the German Gerat 06 (note that it was locked, not roller-delayed). This would coupled with a long recoil gas pistol (the Gerat 06 had used a short stroke piston) and put into a bullpup configuration, chambered for the .280 British cartridge. Interestingly, it was also fitted with a mechanism which automatically dropped the bolt and chamebred a round upon the insertion of a loaded magazine. The basic operating mechanism has plenty of promise, but the implementation in this case was far too complex to have survived serious trials.

As NATO trials rapidly approached in the early 1950s, it became clear that the UK could not submit both The Thorpe EM-1 and the Janson EM-2 for testing. The EM-2 was a simpler rifle and more likely to succeed, and so the EM-1 was dropped from development and all efforts concentrated on the EM-2.


  1. Nice long barrel, reducing the overall length of the rifle, which the bullpup configuration permits enabling 5.56mm to function in it’s most effective manner. It’s pistol grip is somewhat reminiscent of the Fg42 Second model.

    • Compare that to an Sa80, who’s barrel would end approx halfway, in the additional wood grip bit on this. This weapon would be lighter and better. Steyr Aug trigger selector lark, cooking with gas.

  2. I know this isn’t in 5.56mm but the point is, with a 25″ barrel it performs better negating the need to switch calibres which seems alot of work when the increased barrel length would solve it- Not in an M4 obviously as the forward magazine would make the overall length to long you’d end up with an unwieldy SLR type length instead of 6″ shorter with the same barrel length.

    Can’t an M16 be bullpupped? It could if you did that pistol AR trick in regards the return spring.

    • It isn’t too long, look at the pictures of troops with the EM2 strapped across their fronts, way shorter than the SLR.

      • I think the issue is pressing personally, the Russians now have optics and can see us. We need another advantage- Bullpups provide it, increased range over the Ak- If the bullpup has a long barrel. Not that I’m an advocate of Russian fighting, I’m not. I don’t believe in Barry Obamas vision of values- Creating a race of Snowflakes with gender identification issues, who can’t see past their IPhobe.

        But just incase that vision wins through by demographics etc. We have to get real it won’t be a matter of business interests, it would be a big war. We need to drop as many as far away as possible- More of them; Chinese etc, before closing with Bayonets.

        • You don’t need longer ranged rifle, you need real 7.62x51mm light LMG in every squad and 7.62x51mm DMR in every squad. Basically what Russians and Soviets before them had since… 1960s.

    • “Can’t an M16 be bullpupped? It could if you did that pistol AR trick in regards the return spring.”
      Even if it might be technically possible, question: does its worth it?
      Converting from classic to bull-up mean that you must chosen between deep modification or peculiar ergonomics.
      Also why you want to apply such modification for M16, which due to its construction is ill-suited for shortening (see M231 Port Firing Weapon), when there exist others design, like H&K G36 or Bofors Ak5, having smaller issues with that?

      • I do not know about any attempt to make M16 into bullpup. I think you are right when you say it is “ill suited”. It is actually ill suited to what it is and on several fronts, the gas plugged into action standing well above anything, screwy magazine well the next and so on. HKs did make it better but way heavier and obscenely expensive.

        It’s the mental inertia which keeps it going. The only true competition in form of AR18 is not much better either. This 7-lug locking is just sooo finicky (bolt to cartridge engagement is just .04-.05″)… imagine Russians doing something like that!

        Yeah, you have Stg90, but that thing is pricewise totally out of range of reasonable; Swiss watch of guns, but whole thing shakes and rattles at the same time. AK’s winner any and every time.

        • And as for bolt-action rifles, would the Type 99 Arisaka Rifle count as one of the more cost-effective weapons? We can’t get much better than that without resorting to buying up Magnum or Nitro-Express grade big game rifles (the barrel burst when catastrophic over-pressure occurred whereas other rifles would have gotten exploded receivers)…

          • Bolt action rifles are in my mind still the king. They may have missing rate of fire, but in a compact version such as recently featured Steyr Scout, they would do good job. As far as 99 Arisaka rifle, in even more compact version with plastic stock and perhaps semiauto as option with low-power optic would be fantastic. I know I am swimming little bit against the current here, but assault rifles are not used as intended. They are misused/ abused actually. Look as any of Mid-Eastern fighting video, you’ll get the idea what I talk about.

          • “Bolt action rifles are in my mind still the king.(…)assault rifles are not used as intended”
            I think comparing bolt-action rifles vs assault rifles is improper.
            It should be rather bolt-action rifle vs self-loading rifle or sub-machine gun vs assault rifle, as self-loading rifles replaced bolt-action rifles and assault rifles replace sub-machine guns.

        • “only true competition in form of AR18(…)AK’s winner any and every time.”
          I wouldn’t say so, others assault rifles, which are neither AR18 neither AK systems, were adopted, to name few: Beretta AR-70/90, CZ 805 or Bofors AK5.

          • Beretta and Bofors (based on FNC) is dangerously close to AK. CZ805 (basically a flop) and its later iteration 807 are AR18 clones; it is just juggling with some optimisation.

            Note that Beretta controls action by inserted guides which looks like POS. FN were little smarter using guide rods. Still, variation of AK as far as action is concerned.

          • FAMAS and HK33. Both are of course pretty much going away, since FAMAS is being retired from active service and HK33 is no longer offered by HK, although some countries still use it.

      • The Iranians bull-pupped the M16 with their KH-2002. This was copied from a Chinese copy of the M16 (NORINCO Type QC) and then converted to a design that looks a lot like the French FAMAS rifle. It seems that it works, but has not seen much success in the arms market outside of Iran.

        • You are correct with Khaybar rifle, but I would like to know IF they became general issue – I doubt it. Now there is lot of talk about another Iranian rifle, somehow mimicking SCAR. We shall see what they can do, so far not much on their own.

  3. @Ian

    May we expect a video on Jeziorański E.M.1?
    It seems, if I am not mistaken, to be the most obscure among the experimental British (or rather British-Polish) post-war guns, so info on that would be really interesting.



    • “experimental British (or rather British-Polish) post-war guns”
      Now I wonder: does these arms designer worked in that area in Poland before outbreak of war? If so, what their works looks like?

  4. Hi Ian,
    It is complicated but it was so far ahead of the curve I can understand how they got dthat way. I find it amazing that they were even able to get it to function. Cudo’s to the inventors.

  5. I haven’t even watched the video yet. So I don’t need to contribute dubloons… “Incidentally have you seen the price of Dubloons, I was intending to send one”

    • Quite complicated… The gun, sort of Fg42 again but backwards and upside down type thing- The firing mechanism. Still it was a bullpup.

      Great gun, gone are the days. “World wars aren’t beneficial obviously” well… I mean, morally etc.

  6. Odd that they would go for a gas piston operated roller locking when it was already proven that roller delay worked.

    • The gas piston gave more of a delay, perhaps .280 was different to 7.92 short in the impetus of the duration etc.

      The g3 worked in 7.62 Nato obviously- Weight perhaps… Although this piston etc doesn’t look light. Happen they hadn’t realised at the time I.e. The g3 came later.

      • I bet it was fascinating at the time.

        How about a Browning M2 bolt, which is modified at the front to incorporate shaped surfaces effectively making it a bolt carrier, in order a roller head can be attached as the bolt. In conjunction with a separate pair of shaped surfaces acting from the front against the same pair of rollers via them being attached to a gas plug running beneath the chamber by way of a port forward of the cartridge mouth.

        This would negate the need for a 12kg or so mass to act as the carrier against the bolt in a so delayed system, in that calibre. While providing the initial delay before gas added to it, to accommodate the gap “duration” between the two- Enabling a gas delayed blowback.50 BMG.

        You then extend the M2 to accommodate the change, enabling a fixed barrel lightweight version to be arrived at.

        Two shaped surfaces see, mass and gas.

        • Guided rounds are the future, along the lines of Exacto. And I doubt if they can ever fit into 7.62mm.

          Weight vs Accuracy.

          Nobody is removed from the theatre of operations if the round doesn’t hit, so surely rounds which hit are the future regardless of weight I.e. 1 new round hit, 3 round miss… Lightweight non hitting rounds don’t balance this out E.g. 3 rnds may weigh the same as one, but with accuracy- One would hit.

          This is regardless of robots.

          • BLAM!!! Accuracy, the bullet is powerful enough to give most of these robotic man sized solutions a bad day. It will bust right through them- Leaving a ten thousand dollar wreck.

          • “Guided rounds are the future, along the lines of Exacto. And I doubt if they can ever fit into 7.62mm.”
            Using guided projectile, would be easier to implement in bigger, also with such change, it would need over-think of some ideas – as guidance system mean that better accuracy might be achieved with smaller muzzle velocity, so heavier (possibly bigger caliber) projectile might be used for same recoil.
            It also give possibility of rocket-assisted projectiles.

    • Gas operation with a locked breech is much easier to get to run and is (slightly) less fussy about slight variations in bullet weights and pressure curves compared to a delayed blowback.

      On the down side, the gas system introduces more weight and more machining and expense in manufacturing

      For ergonomics, gas operation can spread the felt recoil pulse out over a longer period of time, giving less felt recoil compared to a delayed blowback.

      Hoping that this helps

  7. As a man much more interested in history than guns, I need to come back and watch this again with my phone; so I can check the given references.

    As Jim Kelly says: ‘…so far ahead of the curve.’!

    In the late 40’s the UK were at the sharp edge of many things, including space flight, but didn’t have enough cash for enough coal to keep every warm in winter! How could we pay for the creation of this massive IQ needed to strip, MENSA, gun?

    Who said: “Spend more god on making a more complicated! gun”?

  8. This design is perfect visualisation of British mind… never straight forward and always “unique”; whatever the cost may be.

    • Beer kegs.

      As electric car batterys… Pull out, drop in.

      Save recharging, the future? Or are we fighting for no future.

        • I was so lucky to work with both British and German people at various times; they both impressed me in some way. One time there was a crusty middle aged German fellow and young English guy, bit cocky as you’d expect, in same office. The German fart used to pick on the other fella’s ways by his usual comment: “ah, now I got it, this is English way to fly”. His opposite greeted him daily: “watcha-cock!”. Eventually the German found liking in it and they greeted each other in unison.

      • Have you seen the two Russian teenagers video of them playing with four magnetrons from microwave ovens in an array around a commical looking trumpet?

        Microwaves are quite effective against unshielded circuitry, and might even be able to shoot down midges and blowflies at close range…

        Anything bigger than that has too much heat capacity (it takes minutes to get enough energy in to heat a few ounces of potato).

  9. I’m going to have to look at the manual, to remind myself how the back to front striker cocked itself.

    A slight nit pick on the description of roller delay blowback,

    The delay comes from the inertia from accelerating the rear part of the bolt

    The combination of the slope of the rear of the roller seats in the trunion and the angled nose on the rear of the bolt that comes up between the rollers from behind and seats the rollers into the trunion, gives somewhere around a four times gearing up ratio between the front and the heavy rear of the bolt.

    The complicated bit is matching angles and the weight of the rear of the bolt in order to get the desired speed of opening with a particular bullet, load and barrel length.

    Not too fast, or cases will burst and the buffer will get hammered to bits.

    And not too slow, or it won’t work as soon as it gets any dirt and gum in the action.

    A gas piston and actual locked breech should make the process of getting the gun to run, much easier.

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