Modern Historical Intermediate Calibers 022: The 7.92x40mm CETME

"First generation" intermediate calibers together. Left to right: 7.92x33 Kurz, 7.62x39 (commercial lookalike standing in for M43), .280/30 British, 7.62x45 Czech, 7.92x40 CETME, 7.5x38 Swiss.

"First generation" intermediate calibers together. Left to right: 7.92x33 Kurz, 7.62x39 (commercial lookalike standing in for M43), .280/30 British, 7.62x45 Czech, 7.92x40 CETME, 7.5x38 Swiss.

We haven’t done a Historical Intermediate Calibers post in a while, mostly because most of the stuff that’s interesting enough to cover is difficult to find real world examples of. Today, we’ll be looking at one round I had planned to do ever since the series expanded beyond the original seven rounds covered, but of which I hadn’t been able to find a physical example until recently. Most of what I’ll call “first generation” intermediate rounds (although they aren’t truly the first) owe some debt to the German 7.92×33 Kurz caliber developed in Nazi Germany, but today’s round is truly its heir. After Nazi Germany’s capitulation in World War II, Mauser’s engineers fell into the hands of the French government, who set them to work developing weapons for French forces, including carbines based on the roller retarded blowback StG-45 assault rifle. Unhappy with his work in France, Ludwig Vorgrimler, who had worked on roller blowback firearms since before the Nazi surrender, left the country in June of 1950 and moved to Spain, where he began working for the Spanish Centro de Estudios Technicales de Materiales Especiales (CETME), who were responding to an ambitious Spanish military requirement for a new assault rifle. The weapon had to be less than 7 pounds in weight, controllable in the fully automatic fire mode, and have a maximum range of 1,000 meters. To meet this requirement, a former Luftwaffe ballistician named Dr. Gunther Voss came up with a unique idea: A new projectile with an aluminum core and gilding metal cladding, which would be very lightweight, yet very long and with a relatively high ballistic coefficient. The gilding metal cladding was ingenious, as it gave the bullet high rotational inertia, similar to a flywheel, which ensured it would remain stabilized throughout its flight, despite its extreme length.

I do not have data for the ballistic coefficient or form factor of the resulting 105gr (6.8g) 7.92mm CETME bullet, so the data below is an educated guess on my part using an estimated 0.76 i7 FF, which is exceptionally good. Anecdotally, this bullet was supposed to have a ballistic coefficient similar to the 7.62mm NATO’s projectile (0.200 G7), which suggests this estimate is essentially correct.

On to the graphs:

wVv7Rfg 3dQ5SCM PZtY2mc kwZTGrb

These graphs indicate that the Voss bullet concept did exactly what it was designed to do. With respect to velocity, drop, and drift the 7.92×40 CETME dramatically out-performs the 7.92×33 Kurz, and nearly matches the 7.62x51mm NATO. Only with respect to energy does the CETME round fall short of the 7.62mm, although it still performs better in this respect to either the 7.92×33 Kurz or the modern 5.56mm M855.

In terms of weight, the 7.92×40 CETME scores well, being every bit as light as other brass cased full-caliber “Kurz” type rounds, at 17.5 grams per shot. It does not, however, compare well in this respect to more modern SCHV calibers┬álike the 5.56mm, which weigh 12 grams per round.

The rifle that Vorgrimler designed and that fired the 7.92×40 CETME lived on and became what is known today the “CETME rifle”, and which was also slightly modified to become the world-famous Heckler & Koch G3. The caliber itself, however, didn’t, nor did its innovative flywheel-esque stabilization concept. A very similar idea would crop up again later, though, with the 5.56x38mm FABRL round developed by Frankford Arsenal in the 1970s.



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 can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Awesome, thanks for the write up. I’ve always been curious about the 7.92 CETME.

  • Giolli Joker

    Interesting.
    That bullet could have some commercial success, maybe in long range varmint hunting like the Liberty Ammunition we’ve recently seen on these pages.

    BTW, I’m happy that the pause on this series has ended. ­čśë

  • Patrick K Martin

    Thank you, I needed this for one of my new books

  • Tassiebush

    Wow this round has a lot of concepts that seem like they would be worth revisiting.

  • FWIW: Gunther Voss was also the father of the loffelspitz spoon nose projectile used in the CETME/HK 4.6x36mm and HK’s later 4.6x30mm PDW cartridge.

    https://www.google.com/patents/US3357357

    • ArjunaKunti

      We could easily make a full portfolio of rounds for a modern military from G├╝nther Voss’ children:
      -4.6×36
      -7.92×40
      -9×85 MEN

  • gunsandrockets

    Wholly original case? Or based on something else?

    • Based on 7.9mm German.

    • Secundius

      “Spanish Kurz”…

  • Aono

    So why did this concept fail? Is it because the flywheel essentially precludes a penetrator?

    Very interesting, thank you once again!

  • ArjunaKunti

    This concept can be revised in modern calibers for example in 7.62 NATO. With a EPR type steel penetrator tip and after that a thick brass jacket filled with plastic or tracer material. It would be interesting to see that how much this could improve the performance of modern rounds.

      • ArjunaKunti

        No, this round has a full aluminum core. I think it would be more economical to make it with plastic but to put a steel penetrator to the tip.

        • Oh, that bullet construction was used on the 5.56x38mm FABRL. In 7.62 caliber that bullet would weigh 96gr and have a 0.173 BC, which isn’t bad. If Powley is to be believed, you could get about 3,200 ft/s with it from a 16.3″ barrel, so that’s nice. Retained energy at a kilometer would be a bit disappointing, though, about the same as 7.62×39, because the round spends so much of its time in the supersonic flight regime.

  • roguetechie

    I’m even more convinced after reading this that the 7.92×40 and 5.56×38 FABRL need to be investigated. I especially like the way that it seems to give more ranged performance without having quite the high energy level associated with 7.62 NATO. Maybe this step down in energy will be enough to make controllable fully automatic fire more controllable from shoulder arms when needed.

  • Thamuze Ulfrsson

    man, I’ve love to see this round or an equivalent thereof pop up in competition to all those happy-fun-time .30 cal ARs. Maybe adjusting the case length a wee bit x45 or x48 instead of just “x40”. Could be a rad AR-10 chambering option, y’know?

    • politicallyincorrectshooter

      was thinking of a four column magazine in a 7.62 by 51 length magazine while using either the case from either the 556 or the 5.6 by 50 Magnum but I don’t know if the extra length would fit. A smallish steel penetrator set into a hollow aluminum body might work, using the aluminum like a ballistic cap…

      • Secundius

        If the “Inference” is Towards the 5.56×45 Nato Magazine? I’d say Yes! Anything Else, I Can’t Say with Absolute Certainty…

  • politicallyincorrectshooter

    Has anyone managed to find info on terminal performance? I suspect as it tumbles it would be devastating.

  • Spanky

    No mention of the .300 Blackout? Pretty much an equal to the 7.92X33 Kurtz.

  • CavScout

    Do we really have to say ‘Nazi Germany’ ever damn time? Or ever? Does it matter who ruled at the time? Sadam Iraq? Obama United States? Mr Mogato Japan?

    Sorry, just seems like PC bull.
    I might truly be wrong on this, but I believe the name of the country, even back then, was just Germany. (deutchland or w/e, sure)