Historical Personal Defense Weapon Calibers 015: The 7.65x20mm French Longue

Right to left: .30 Pedersen, .30-18 Browning, 7.65x20mm French Longue, .32 ACP, 9x19mm Parabellum.

In this fourteenth installment of Personal Defense Weapon Calibers, we’ll be looking at a highly minimalist incarnation of the PDW/SMG round: The 7.65x20mm French Longue. The story of the French Longue begins with the US entry to World War I and the brilliant inventors John D. Pedersen and John Moses Browning. Faced with the stalemate of trench warfare, these designers were tasked with finding a solution in the form of handheld autoloading weapons. Both came up with semiautomatic rifles firing small, low recoil .30 caliber rounds. Pedersen’s “Device” converted a standard M1903 rifle into a rapid fire semiautomatic, but it was Browning’s autoloading rifle and its .30-18 round (very similar to the .30 Pedersen used with the “Device”) which caught the eye of the French Ordnance officials. The .30-18 Browning, as it is called, was evidently cloned to become the 7.65x20mm Longue used with the interwar French Mle. 1935 pistols and MAS-38 submachine gun.

Left to right: .30 M1906 Ball, .30 Pedersen as would have been issued in 1919, .30-18, 7.65 French Longue, and modern production .32 ACP and .45 ACP for scale. Note how incredibly similar the 7.65 French Longue and .30-18 cartridges are.

 

The 7.65 Longue was a fairly modest round, being in approximately the same class as the 7.65 Parabellum and 8mm Roth-Steyr, but more powerful than the .32 ACP. The resulting round fired a 77gr (5 gram) bullet at a muzzle velocity of about 350 m/s (1,148 ft/s) from the handgun, and 380 m/s (1,246 ft/s) from the longer barreled submachine gun. Its ballistics are given below:

Judging by the graphs “minimalist” may be a nice way of saying “woefully impotent”; the 7.65 Longue has the worst velocity, energy, and drop characteristics of all the rounds it is compared to here. However, it is notable that beyond 200m even it retains more energy than the high velocity 5.7mm round, illustrating the deleterious effect that high muzzle velocity has on such low energy rounds over moderate distances. In trade for its lackluster performance, though, the 7.65 Longue is at least quite light, at 8.6-8.7 grams per shot, compared to 12.6 grams for 9mm M882 and 20.9 grams for .45 ACP.

Still, the 7.65 Longue was at least briefly considered adequate for its intended purposes, and submachine guns in this caliber continued to be used by the French Army into the 1960s when they were finally completely phased out in favor of higher performing 9mm weapons like the MAT-49. Although automatic machine pistols have been made in smaller calibers, those weapons were not really intended to be used at ranges above more than a few meters, no different than semiautomatic pistols in that respect. In this way, I suppose we can consider the 7.65mm Longue “the smallest practical submachine gun round”.





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 nathaniel.f@staff.thefirearmblog.com.


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  • No one

    More proof that we need a real mans round and not a warmed over .32 ACP Poodle Shooter like the 7.62x51mm

    WAKE UP US ARMY!

    • TJbrena

      .375 H&H is the bare minimum for reliably stopping men (and rhinos).

      • iksnilol

        I dunno man, odd numbers give me the heebie jeebies.

        .600 N&E is the minimum, besides no awkward odd numbers.

      • Brett baker

        .45-70-500. The last stopper the us ever issued.

  • Edeco

    Oh yes – I’ve said here before I’d love to see 7.65×20 come back. Maybe longer and warmed up. Either way now that many pocket guns are locking-breech it beats 380 and 32 in a few ways.

    • Matthew Groom

      I designed a wildcat for my 1935A&S pistols I call “The .303 Liberty”, where the case is lengthened to 23mm, designed around the 60grn Speer Gold Dot for 32 ACP. Loaded to 9mm +P pressure (38.5kpsi) it generates around 375ft/lbs of muzzle energy from the 4.3″ barrel of my 1935A. It’s conceptually based on a lengthened 7.62x20mm Longue case, but the version I settled on was based on a shortened 30 Carbine case. Some brands of 30 Carbine brass fit in the magazine, but others are on the max specifications for the base diameter of .30 Carbine won’t fit. Also, you lose 1 round out of the magazine in some of the mags I have with this conversion. I have not converted my 1935S to it, because its barrel was in better shape. Converting 32 Long brass to rimless is a massive PITA.

      • ARCNA442

        Ever do any gel tests with that cartridge?

        • Matthew Groom

          I actually contacted Brass Fetcher about having them do an impartial gel test on it, but I was trying to get the company I worked for to pay for it, and they weren’t interested in it, so I never did. I shot it in a couple of local IDPA matches, but I was paranoid about losing my brass!

      • Edeco

        Wow, great project. Your 303 Liberty sounds like it would be good for everything from pocket guns through duty guns and SMG’s.

        I recall a guy on a forum doing a 30 Carbine based wildcat in a Kel Tec P32. Searched but couldn’t find it.

  • Matthew Groom

    I feel like the French dramatically under-loaded this cartridge for use in lightweight blowback actions, like the MAS 38. This makes sense when you look at how small, and subsequently light the bolt on the Pedersen device was, but it seems ludicrous when used in a well-built, locked breech handgun, like the SACM 1935A and the MAC 1935S. Based on the CAM models I drew up years ago in Solid Edge, it appears that either design could easily fire 40kpsi chamber pressure loads (slightly higher than 9mm +P+) before significant plastic deformation of the brass during cycling might lead to problems. A modern, commercial load at 25k-30kpsi would make the .30 Longue a better cartridge than the .380 in terms of energy.

    Also, consider that this case originates from the .32 S&W Long family of cartridges, which eventually gave birth to the .32 H&R “Magnum” (loaded to 38 Special pressure and length), and the .327 Federal Magnum (loaded to .357 Magnum pressure and length), it shows that the web of the cases can easily handle higher pressures than the French loaded it to (around a pathetic 14kpsi according to Quickload).

    We shouldn’t judge a cartridge based on a single loading; this would be like judging the 9x19mm based off of the 9mm Glisenti.

    • Agreed, I’m curious what 7.62×30 would do loaded at 42kpsi (9mm +p+ / 9mm Major levels.)

      That being said, it’s hard to imagine it outperforming a .30 Luger +p+. And then of course with swept bore volume, it’s hard to imagine .30 luger +p+ outperforming 9mm +p+ with the same projectile weight.

      For example, Underwood’s new 65gr 9mm +p solid copper is doing 1800fps. We’d likely see 1900fps with a +p+ load.

      • Matthew Groom

        I believe that it would perform quite well, perhaps besting old favorites like .38 Special and .380 ACP, but I do not believe that it would match a higher capacity case, like the .30 Luger. It would, however, allow for more rounds in the same length magazine, and it would also produce less muzzle pressure and noise, which may be one reason why the French adopted it like that (no earplugs back then).

    • Hey, I’m just going off how the round was actually loaded. I do think you could do quite a bit better with a hotter load. A “7.65 Longue +P+” might make a dandy little PDW round, certainly.

      • snmp

        BTW, the firt protype of MAS 38 (SE MAS 35) were build in 9x19mm

    • snmp

      MAS 38 is delay blowback Off-axis bolt travel

      • Matthew Groom

        That’s to reduce felt recoil, and only slightly; it doesn’t qualify as delayed blowback, despite what is written on Wikipedia. There is no bearing surfaces, rollers, caming blocks, or other devices that “delay” the blowback to any significant degree.

        • snmp

          “In this action, the motion of the bolt is not along the same
          axis as the barrel. Hence, when the bolt moves backwards, it moves along an inclined place placed at an angle compared to the barrel and thereby has more resistance to backward motion without increasing the bolt’s weight correspondingly. This allows the weapon to have less recoil and less muzzle climb when firing in automatic. This mechanism has been used in some modern firearms as well, such as the TDI Vector submachine gun manufactured in 2009 and the Finnish Jatimatic submachine gun made in the 1980s.”

          • Matthew Groom

            6° is not going to have any effect. The Vector uses a complex steeply downward recoiling system that’s around 60°, or about 10x more steep. The “Bliss Lock” on early Thompson SMGs was called a “delayed blowback”, too.

      • Matthew Groom

        That is incorrect; the off-axis bolt travel does not impeed the opening of the action in any significant way, and the only delay to opening of the action upon firing is bolt mass. There is no roller, cam, or lever mechanism or device, gas retardation, or additional friction point. Therefore, it is a conventional blowback.

  • ARCNA442

    This round has always made me wonder about the practicality of a modern straight walled .30 pistol cartridge. If you could make one with reliable hollow points it seem that you could further increase capacity and reduce recoil and do to 9mm what 9mm did to .40.

    • El Duderino

      Could work…I think the main issue with small caliber/high velocity handgun chamberings is they lose too much in a compact or subcompact platform. They get really flashy/noisy and the velocity drops quickly. It’s why you don’t see any 5.7×28 subcompacts in the local Bubba’s Bang-Bang & BBQ Barn.

      I think a 100gr .32 with a long case blazing out of a 5″ barrel at 1400-1500fps would be awesome, pretty much a medium bore magnum.

      • ARCNA442

        I’m not really thinking SCHV but the minimum required to get a hollowpoint to expand to ~.50 or so and penetrate past 12″ out of a 4″ barrel. Something closer to ~80 grains at 1200 fps like the 7.65×20.

      • Samuel Millwright

        A smaller caliber version of that “bullpup pistol” design could probably get you the bbl length needed to be useful

      • Amplified Heat

        Yes, I suspect it could; perhaps, some sort of miniaturized M14 action could host such a round…though I think a 110gr round nose going 1990ft/s would fit the bill even better 😉

        • El Duderino

          I’ve shot an Automag III. Grip like a VCR tape and split yer eardrums even with hearing protection. I’m thinking of tamping that down by a quarter or a third here…

      • politicallyincorrectshooter

        Do you mean a rimless.327 Federal?

        • El Duderino

          Pretty much.

      • demophilus

        IIRC, you can get that kind of performance hot loading .30 Luger, or rolling your own .30 Carbine loads for the Ruger Blackhawk.

        The .30C Blackhawk been in production for a long time; don’t know that I’ve ever seen a used one for sale. Maybe folks tend to hold on to them.

    • Samuel Millwright

      7mm penna is basically this and it produced pretty crazy mv’s / has more than a little potential, especially if you made something like those EPR style barrier blind rounds shown with the gen 5 glock the other day!

      It’s definitely on my list of stuff i want to work up, but not until i can make my own jacketed projectiles to fire out of it.

    • Matthew Groom

      I designed and built a “super 25 ACP” PDW cartridge years ago that was 9x19mm length to compete with the 5.7×28 (which is just a stupid design). It easily beat the 5.7 in terms of energy with a 35grn Gold Dot, but it was LOUD AS F___! Even out of my 9.25″ Thompson Contender test barrel, it was unpleasant with earplugs on an indoor range. Therefore, I abandoned the project, after about $1500 of investment in materials. :-/

      • ARCNA442

        That sounds interesting. What brass did you use? And did you do any gel testing?

        • Matthew Groom

          It was based on a rimless conversion of the .22 Hornet case, which had the smallest base diameter of any conventional centerfire cartridge. The .25 ACP is semi-rimmed in part because you really can’t make it truly rimless without compromising the primer pocket strength. Converting 300 .22 Hornet cases to rimless on a manual lathe was a special kind of hell, however.

          I never did gel testing, because my boss wasn’t interested in my wildcat designs.

          • Miguel Raton

            “Converting 300 .22 Hornet cases to rimless on a manual lathe was a special kind of hell, however.” — ?? I don’t get it. A pot-chuck, a lathe stop or two and some negative rake tools and you should be g2g. Not saying it wouldn’t take any time, but any time spent turning is better than time spent doing something boring, like fishing or listening to talk radio… %-p
            ;-D

          • Matthew Groom

            Used a collet; wasn’t mine, so I couldn’t ream it to size. Used a stop, but every case was a different length, and found it was easier just to use the rimless profile tool to cut each one to length rather than trim each one slowly to length on a case trimmer. Wore out an RCBS Trim Pro during this project, too. Clamping force was easy to get too high, crushing the case, or too low, spinning and crushing the case. Fortunately, my profile tool was fairly stout, and chipped, but never broke.

            Likewise, cutting the rim required finesse, since going too fast would cause the cases to twist, collapse, and break; going too slow caused rubbing/chatter. I don’t think I could have done a better or faster job on a CNC, nor do I feel like reaming the collet to size would have helped very much, since I was gripping so close to the web as it was.

            Since this project, I have seen a number of similar jobs done using Lee Zip-Trim

    • The most modern version of the concept was the 7.92X24mm VBR – a .30 carbine case shortened to allow working in 9×19 conversion pistols. Loaded to high pressure (38-46kpsi from what data I’ve been able to find) and combined with VBR’s custom AP brass bullets, it was an interesting PDW round. A 19rd 9mm magazine would hold 21 7.92’s, and a 33rd mag would hold 37.

      https://uploads.disquscdn.com/images/87e8d13194bdab31aee0778be8171ddbc7a5c20f7daf309aa63f32e3f6151a13.jpg

  • El Duderino

    “Pistols and Correlation to Winning Wars Beginning with WWII”

    French had the weak 7.65×20.
    Germans had the 9×19…and beat the French.
    Soviets had the 7.62×25 and the U.S. had the .45ACP, and together we beat the Germans.
    The Japanese proved no issue with their puny 8mms vs. the comparatively gigantic .45ACP.
    The muzzle energy of the 7.62×25 and the .45ACP are similar, thus we entered into a 45 year stalemate, which decidedly started to go the U.S.’s way once the Soviets adopted the weaker 9×18.

    My military history doctoral dissertation outline…thoughts? 😀

    • Samuel Millwright

      I want to hurt you right now…. Mostly because you actually have a point…

    • snmp

      in WWII French have in 1939 :
      32 ACP Ruby pistol
      8mm Revolver (Model 1892 + spanish copie of S&W & Colt Revolver)
      9 mmX19 for offensive SMG : EMP36
      7.62×20 for Pistol Model 1935 (A & S version : fathers of the SIG P210)
      45 ACP : 1911 & SMG Thomson 1928

      German have 9×19, 7.63×25 Mauser (same case than 7.63×25 TT), 32 ACP (Walter, Mauser, Sauer …), 44 russian /11,06X25R m Reich Revolver …..

      • El Duderino

        SAFE SPACE! SAFE SPACE!

      • Out of the Blue

        But how many 1911s and Thompsons did the French actually have? I’m pretty sure most of them were nowhere near the Ardennes. Then again, that was also true of the French Army.

        • snmp

          French army in 1939 are more SMG than British arms Force, American arm force and German

        • Kurt Akemann

          The French did do their part in stopping the German ‘Nordwind’ counterattack in Lorraine.

          • Out of the Blue

            Fair enough. They may have been overrun, but many of the French never gave up. The Vichy government is another matter.

            On related note, from what I have heard the French tanks of the era were actually better hardware wise than the Germans. The German ones had better coordination and tactics that capitalized on their mobility. That and lack of coordination between the French air and ground forces allowed the Luftwaffe to pick off their tanks.

    • ARCNA442

      It could be a sign that the country willing to spend resources on such an insignificant weapon has a more robust arms industry.

      • El Duderino

        Could be. Lots of romanticism around military handguns in the U.S., but yeah it’s right above the E-tool and bare hands on the TOE.

  • SPQR9

    The 1935A pistol is fascinating to field strip. It was designed by Petter who would give the Swiss the beautiful P210. But it’s trigger is horrible. The cartridge is a pain to obtain, custom loaders in the US usually lathe turn .32 S&W cases to fit.

    • Amplified Heat

      Yup, clever, beautiful, extremely comfortable little guns. Did I mention little?

    • Matthew Groom

      My 1935A has a remarkably good trigger for a milsurp pistol from that era. I have heard others tell of awful triggers on them, so I wonder if some are better/worse than others?

      • SPQR9

        Well, its a neat design built by illiterate peasants kidnapped as children from Languedoc.

        • Matthew Groom

          Que?

  • snmp

    MAS38 SMG was an PDW (for Self Defense Of Officer, Radio, Trucker, … ) with an rpm of 600, build for Praticable accurancy of 100 m with max to 200 m

    • demophilus

      Good point; 7.65x20mm was more of a PDW cartridge.

      IMHO, it was also influenced by the French experience with the Ruby pistols in the trenches of WWI. They issued a lot of those; some of them must have been used and found wanting. IMHO, the French wanted something a little more powerful and flatter shooting than 7.65 ACP that they could also put in a full auto platform.

      • snmp

        French in 1939 use commercial Volmer Erma EMP36 in 9X19mm (from spanish republican – around 3000) as offensive SMG

  • Amplified Heat

    Imagine a MAS38-style SMG that uses the Browning 1921 patent hesitation-lock recoil-operation principle. You’d have a very small platform (see Forgotten Weapons on that gun to see how it’s like a 2/3 scale of a 9mm SMG) with a decently powerful/ranged cartridge, that has very low axial recoil, and vertically-reciprocating parts that counteract muzzle rise. And the round would be small enough to deploy very high capacity magazines that are still practical in size (scale down a Suomi or SITES Spectre coffin magazine). Oh, and the barrel would be fixed so it’d be ideal for suppression (and the hesitation lock is uniquely unaffected by back pressure, as far as it over-driving the operating parts to excessive velocity anyway)

  • marathag

    , I suppose we can consider the 7.65mm Longue “the smallest practical submachine gun round”

    No love the the 22rimfire from the American 180?

    • We covered .22 Magnum before, which is ballistically similar to the souped up .22 rimfire the American 180 used.

      But I am not sure anyone really considers the American 180 to be a viable battle weapon, anyway.

  • Interesting. My data comes from Альбом конструкций патронов стрелкового оружия (Album of Cartridge Designs for Small and Large Caliber Automatic Weapons (from 6.5mm to 37mm)) by Dzerzhinsky (1946).

    • I think the specs from 9×19 NATO may be a bit high for modern ammo, which seems to be getting progressively slower.

      Per Buffman’s most recent testing of Winchester 9×19 NATO, it is averaging 1,267fps from a 7.72″ CZ Evo. 124gr German MEN is clocking 1213fps from the same barrel. S&B 124gr is clocking an abysmal 1168fps. Norinco 124gr avg 1285fps. Privi averaged 1200fps.

      Only the L7A1 Hirtenberger approached 1400fps, at 1343fps avg.

  • Pro

    I want a modified shield 45 , double stack with 15 rounds of .32x25mm 85gr gold dots (flat base mag) doing 1250 fps out of a 3.3″ barell for ccw…. And the same pistol with a 4″ threaded barell doing 1320 fps and a longer 20 round mag with mag sleave for duty/tactical work….

    • Edeco

      Also a G17L with a giggle switch and that cartridge. Would expect it to be way more controllable than a G18 with higher ME and hold 8% or so more rounds in an equivalent mag. If going carte blanche with the mags, could make the grip some combo of skinnier or stiffer.

  • Miguel Raton

    From the graph, it appears that it fails to deliver the 275J [200#ft] minimum energy threshold at any range beyond 50meters. Next!

  • CavScout

    Picture caption… “Right to Left”
    Whose right to left????