Modello 1928 Tromboncino Grenade Launcher

In 1928, the Italian army adopted a rifle-mounted grenade launcher. It was a potentially interesting weapon which wound up being fatally handicapped by the use of ineffective grenades. The basic idea was to mount a second rifle receiver to the side of a Model 91TS carbine, but with an integral grenade cup instead of a barrel. The trigger of the carbine was modified with an addition linkage to operate the sears on both receivers. When firing a grenade, the bolt would be removes from the carbine receiver and installed into the grenade launching receiver.

The most unique part of the design was in the grenade cup. Instead of using blank style grenade cartridges, the Tromboncino used standard ball ammunition to launch grenades. When the round was seater in the chamber, the front of the bullet was held firmly in place by a threaded plug in the front of the chamber. Upon firing, the bullet could not move forward, so the neck of the case would burst open, venting the propellent gas around the bullet and through vent holes into the base of the grenade cup, thereby throwing the grenade.

This system was quite clever, as it did not require any special ammunition types but also did not require designing a grenade which was capable of safely catching a fired projectile. However, the tactical use intended was for troops to use grenades in the immediate opening of a close assault, and so the grenades were designed to be concussion type more than fragmentation, to ensure that they could be used in relatively close quarters without injuring the firer. The result was a grenade design which was not effective enough on the enemy to be of much actual use, however, and most of the Modello 1928 carbines were decommissioned in the mid 1930s.


  1. Very interesting.

    The launcher and host rifle have survived in surprisingly good condition.

    Was there originally a partial block in the magazine port of the launcher receiver to aid lining up the cartridge?

    Also, were the launcher receivers recycled from earlier rifles? Or taken from new production?

  2. Greetings everyone,

    First, some links (unfortunately only in Italian – drop a line if google translator cannot be of help) about the device in question, plus some other Carcano’s grenade launchers: (User Manual) (“BATTAGLIONE 1928”)

    The Regio Esercito, being VERY stingy, probably liked this device as it was seen as a way to recycle out of specs Carcano actions; this veniality probably concurred to the lack of a second bolt too.
    Official documents states it was dismissed for it inaccuracy as chief reason (1930 edition of ‘Nozioni sulle armi portatili, sugli esplosivi, sulle artiglierie e sul tiro. Parte I. Materiali’ published by Regio Esercito’s General Staff has it already stricken out), but the dire need of firearms during WWII brought them out of the depots – probably with very limited to no ammution.
    Best Regards,

    • “drop a line if google translator cannot be of help)”
      Does I understand correctly User Manual in that whole mass of weapon is 4,780 kg and of grenade is ~150 g?

      • Yes, the weapons system weights 4,780 kg (roughly 1,680kg more than the standard Moschetto TS). The training grenade (Inerte = non explosive, wooden dummy core) is 150g, while the explosive one is 160g (it’s listed in one of the other sources).

        • Under Section 5 of the User Manual, the safe area to be cleared for use of training grenades has to be 400m x 200m. Which such wide lateral spread, probably it had been realized how under combat stress it was practically impossible to hit anything, and with low powered grenades, even in the case putting it out of combat. The side mounting imbalances the rifle too. Having the two actions linked together to the same trigger, with one of each completely exposed at any given time, is another potential issue, as sand/dirt/mud could enter it, block the trigger bar thus rendering both the GL and the rifle dead.
          The Brixia 45 mm mortar was a far more wise choice: its section could provide more rounds per minute, more precisely, at a longer range while requiring comparatively less manpower (and in fact it was much more appreciated than Breda 30s).

    • “The Regio Esercito, being VERY stingy, probably liked this device as it was seen as a way to recycle out of specs Carcano actions; this veniality probably concurred to the lack of a second bolt too.”
      Stingy always pays twice
      But if they make it as cheap as possible, wasn’t rifle grenade similar to MARTEN HALE Mexican grenade better?
      it wouldn’t need 2 bolts and I presume rifle with well-worn barrels might be used, the problem might be with cartridges as it would need blanks.

    • From the images and descriptions it seems (with my very limited Italian and funny Google translations put together) that the live grenade was pretty much a standard fragmentation grenade and not a “hybrid” one. There seems to be no information about the amount of high explosive in the grenade, nor type of HE (I would guess Amatol), but in general rifle grenades like this don’t have enough HE to be effective as any kind of concussion grenade¹. The designers should and would have been aware of that fact, so in my opinion it is a “normal” fragmentation grenade.

      ¹ Concussion, or “defensive”, hand grenades are typically big cylindrical things and weigh significantly more than fragmentation grenades. Most of their mass comes from the high explosive. Their weight means that they can’t be thrown very far, but since they are for defensive use, that is really not an issue.

      • ““defensive”, hand grenades are typically big cylindrical things and weigh significantly more than fragmentation grenades”
        Wait. I though offensive grenade have more HE filler, when defensive have less HE, but produce heavier shrapnels and thus have bigger lethal radius.
        Example of defensive grenade is F-1 (used by France during First World War).

        • Right. And the “petard” or Thouvenin offensive grenade had a light sheet metal body, and was lighter so it might be thrown further. These were carried in sacks and the “game pocket” of the snazzy uniform jackets favored by the Arditi/Stoßtruppen… The idea that as attackers they didn’t have much in the way of cover, so tossing an explosive into a trench, dugout, bunker, or blockhouse would accomplish its goals of killing or driving out enemy personnel, but with less fragmentation.

          “Defensive” hand grenades rather assumed that one was in a trench, foxhole, or similar fighting defensive position, and that the excessive lethal radius of the fragments on a heavier grenade would be more dangerous to exposed attackers than covered defenders…

          Offensive grenades include things like the German “stick grenades”–although, obviously, the defensive “kugel grenade” of WWI with its cast-iron body was often attached to a stick, just as the “hair brush” extemporized nail-bombs… The aforementioned Thouvenot, and some others… RGD-5? vs. Soviet version of French F1?

        • My error, sorry, it should be:
          OFFENSIVE – more HE, smaller lethal radius
          DEFENSIVE – less HE, bigger lethal radius

          • Defensive: for throwing FROM shelter/trench
            Offensive: for throwing INTO shelter/trench

            In addition to be safer for the exposed thrower, offensive grenade’s larger charge is suitable for blowing away barbed wire or generally destroying defensive structures.

        • Yes, you are quite right; when it comes to fragmentation grenades “defensive” means a larger effective radius for fragments, whereas “offensive” means a smaller radius than “typical” throwing distance of the grenade. Concussion grenades can be considered either defensive or offensive (it seems to vary between armies), but in any case they have minimal or no fragmentation effect.

      • The grenade was filled with 32gr of TNT, into an iron case, and with an iron spiral around it to ensure fragmentation.

    • Remember that the development team did not have access to high-structural-strength-with-low-structural-weight synthetic materials for rifle stocks! Nor did they have something like “gun barrel grade aluminum!” Considering that you do not want the grenade launcher to explode in your face, the only way to lighten the carbine is chopping the wood stock away (save for the butt stock) and then adding a skeletal mounting frame to keep the grenade launcher parallel with the carbine barrel. Forget the bayonet lug! Or would you rather add lots of payload in the grenades instead? I could have messed up, but it seems that a mad scientist is needed to fix the system…

      • “I could have messed up, but it seems that a mad scientist is needed to fix the system”
        Firstly, if you want add-on parallel-mounted grenade launcher to rifle, why not make fully breech-loaded system and thus giving possibility of integrated loading, rather than cartridge then grenade?

        • Okay, let’s try it. The first item to address is the grenade, which would require a cartridge casing, complete with primer and propellant. A more potent explosive charge and/or payload is needed as well. The grenade launcher would need a redesigned receiver to accommodate this new cartridge grenade. The grenade launcher will have its own bolt or breech-block and perhaps a separate trigger on the carbine to avoid simultaneous rifle and grenade launcher discharge. Am I missing something?

  3. “did not require any special ammunition types but also did not require designing a grenade which was capable of safely catching a fired projectile”
    Dyakonov grenade launcher also uses normal (live) cartridge and grenade does not catch bullet, but it is different solution, see 4th image from top here (click to enlarge):
    this is cut-away drawing of grenade, when cartridge is fired bullet pass through “hole” in grenade, propelling it (cf. blow-forward principle of operation).
    Unlike Tromboncino it is attached to muzzle of rifle (see 1st image from top), it is rifled (see 2nd image from top) and host rifle is additionally equipped with tripod, which make firing in prone position much easier (see 5th image).
    Additionally grenade has own powder charge (2,5 g) under bottom (again see 4th image from top, gray color), which was removed by crew if short range fired was needed. Effective range was 600 m and 150 – 300 m with charge removed, muzzle velocity 110 m/s and 54 m/s. Mass of grenade was 370 g. Grenades were equipped with time fuse, time can be set up to 12 sec. Lethal radius was 50 m. Mass of rifle and grenade launcher was 8,6 kg, RateOfFire 6 – 8 rpm.
    Immediately before Great Patriotic War, HEAT grenade was developed which can pierce 50 mm armor, but need blank cartridge and has low accuracy; it was used in limited numbers.

  4. The Soviets also had that odd spade/entrenching tool that doubled as a 37mm mortar with the shovel portion as a base plate. Also, like this Tromboncino device, an attempt to provide a sort of short range artillery/grenade-launching device to infantry without further encumbering them with all sorts of “extra” equipment.

    a) USSR–the shovel doubles as a grenade-launcher/mortar, with a bandolier of smallish-37mm bombs (“bomblets?”)
    b) Year VI of Mussolini il Duce–just one kind of ammunition (ball), and only one bolt… No need to put a separate cup launcher on the muzzle like the French Tromblon “shoot-through grenade” (recall, these were used by the USMC in the Guadalcanal campaign, while the IJA and navy had the various “knee mortar” grenade dischargers…). Surprising that the designers did not opt for a “shoot through” or similar design, but then again, with the launcher such a short little thing on the side, the safety of the bullet coming out would be much greater due to muzzle discipline issues… After all, the Tromblon was initially for the rifles the length of the Lebel 1886/93 and 07/15, no? Ditto the Soviet launcher what with the M1891/30 vintovka!

    • “USSR–the shovel doubles as a grenade-launcher/mortar, with a bandolier of smallish-37mm bombs (“bomblets?”)”
      See 1st, 2nd, 3rd and 4th image here:
      (subsequent photos are for modern spate – mortar)
      In Russian service it was known 37-мм миномет-лопата, so it would be mortar not grenade launcher, which also make seems because it works more like mortar (no trigger – just load missile in barrel)

    • “Also, like this Tromboncino device, an attempt to provide a sort of short range artillery/grenade-launching device to infantry without further encumbering them with all sorts of “extra” equipment.”
      If I am not mistaken hand grenades gained popularity during First World War, where it proved be useful in trench warfare, also during this conflict various ancient-technology grenade-launcher were developed like for example Arbalète sauterelle type A, so it is logical that on basis on experiences from that conflict, various grenade-launchers were developed.

      There is also song КАРМАННАЯ АРТИЛЛЕРИЯ from Great Patriotic War, about hand grenades, text:
      it title can be translated as “Pocket Artillery”

  5. Brilliant. Spend the time and money to develop the device without develop a HE AND a fragmentation grenade for it. If it can range out to 200-ish meters, you don’t have to worry much about fragments, right?

    As I understand it, the Brixia mortar was a lot of device for a small payload.

      • The Brixia was optimized for high rate of fire and accuracy. It could be considered a conceptual successor of the WW1 37mm infantry guns and predecessor of the modern automatic grenade launcher. The various 5″ and 50mm mortars of other nations were definitely simpler, cheaper and had a potentially better range, but were much less accurate and had a lower maximum rate of fire.

      • Now imagine to be on the beaches of Normandy, with Germans that shoot at you from small openings in bunkers 100-200m distant.
        Do you prefer to have the British “two-inch mortar”, and hope that one in one hundred bombs hit close enough to an opening to do some damage, or to have the Brixia, and aim at those openings directly?

        • I guess the Brixia would work for suppressing bunkers but a tank with a large caliber cannon or an assault gun (something like the StuH 42) can easily reduce most bunker troops to hamburger. If that’s not enough then call for heavy artillery and attack planes. Did I mess up or miss anything?

          • First, that, with all the heavy artillery and attack planes, the Germans were historically still firing from that bunkers, and that was true for other landings too. It was not an unusual situation in WWII.
            Second, that large caliber cannons are not personal, nor even company level, weapons. A soldier on that beach couldn’t really think “oh, crap! I left my large caliber cannon on the ship.”. It’s obvious that something bigger could do the job, but bigger things tend to be:
            a) expensive, so they are produced and issued in fewer numbers.
            b) not available for the ordinary grunt, so they have to be called, that, even when possible (that’s not granted) is not exactly the same thing as to have them readily available when you are under fire.
            The Brixia had to be considered as a substitute of other small mortar designs, not of tracked veichles, or naval artillery.

          • True, but I made the mistake of viewing the scenario as a commander rather than as the infantryman. If I could get my hands on a rocket launcher that bunker would turn into an oven… and hopefully I don’t wind up with the PIAT instead! Would a Type 89 grenade discharger also work for landing support?

          • What really makes the difference in a situation like that, is if you can really aim with it. With the “tromboncino” you could. With the Brixia Mortar you could (and you could make adjustment shots too). With a knee mortar, a two inch mortar, or a muzzle rifle grenade launcher without specific grenade sights, you couldn’t really aim at an opening in a wall. Those are good weapons vs. trenches and other kind of “open top” shelters.

          • And that’s true for urban warfare too. With the enemies firing from the windows, what can make the difference is the ability to put the equivalent of an hand grenade into a window from 100-150m distance.

  6. During WW1, the French army (and then the AEF) solved the grenade-launching blank problem with the Vivien-Bessiere or VB grenade discharger cup system;

    The principal difference between the VB and other cup discharger systems such as the British Mills Bomb discharger was that the grenade had a “tunnel” right through it to allow the bullet to go through without impedance. In the process, it hit a spring-type firing pin that fired the primer to ignite the grenade’s time fuze;

    This meant that in event of a “dud” round, the grenadier wasn’t stuck with a live grenade counting down in the discharger.

    The American version simplified matters even more by putting the percussion cap primer for the fuze right in the side of the tube, protruding just far enough to be crushed by the bullet’s passage to ignite the fuze.

    The only major drawback to this system over a regular grenade discharger using a blank round was that pointed out by Ian Hogg. Since the rifle was super-elevated to launch the grenade, the bullet went on to its maximum range, which at 30 degrees or more above the horizontal was something like two or three miles.

    Meaning that instead of being able to practice grenade launching on any regular 300 to 400 yard range, they had to do it in some place where there was enough empty space beyond the range (on the order of four miles or so) that the bullets could safely fall without damaging anything, like a farmer’s cow- or the farmer.

    As for the 1928 Trombocino, Hogg was rather cool on the whole idea, observing that the grenadier could only fire grenades or the rifle as Ian stated. Meaning that he had to trans-ship the bolt from the rifle to the GL to do his job, or switch it back to the rifle before he could even think of protecting himself. Hogg opined that “It would take an absolute Houdini to cope with the thing in a fast-moving infantry battle”.

    Overall, Italian small arms design prior to WW2 seems to have blown hot or cold with nothing in-between. Either you got something excellent, like the Beretta Modelo 1938 SMG, or the workmanlike (if hard-kicking) M1934 service auto, or the Breda M1937 HMG with its elephant-gun-powerful 8 x 59mm round, or something that seemed to have been hatched in a night of insane revelry, like the Breda Modelo 1924 or 1930 LMGs- or this thing.

    There seems to have been no middle ground.



    • “There seems to have been no middle ground.”
      What about Breda Mod. 38 tank machine gun? If I am not mistaken it worked reliably and have barrel heavy enough to prevent problems with overheating, but being limited by magazine of small capacity of only 24.

      • Breda Mod. 38 was just a magazine-fed version of the Mod. 37. Not a bad gun at all, but as you wrote, suffered somewhat from the small magazine. Additionally, rate of fire was too low for AA use, but it was still used so on many Italian tanks.

        • I never quite understood why the M38 had that magazine feed, other than possibly reducing firing gas infiltration into the fighting compartment.

          It seems to me that the M37’s strip feed, that put the empties back into the strip instead of ejecting them separately, made better sense in a tank gun than it did on a ground gun on a tripod.

          That said, the M37 was well-liked by the British in the Western Desert, who happily used captured ones against their former owners, due to their reliability, accuracy, and the long reach and serious killing power of that 8 x 59 round, that was ballistically very close to the .300 H&H Magnum big-game cartridge.



          • The problem with using the Breda M37 in a tank turret or casemate mount is that there is not enough space for the ejected strip. The M38 was a more compact package in terms of lateral space and box magazines are less awkward to feed into a receiver than strips inside a cramped armored vehicle that requires a higher reload speed against swarming enemy infantry. Belts may have a higher ammunition count but will need at least 15 seconds to change assuming that you don’t get blown up by a tank hunter first! Did I mess up?

          • I think you are spot on with this one, CD. One more thing to consider is that the M. 38 was often used in double mounts, which would have made strip feed even more difficult to manage (not strictly impossible, but it would have required left handed feed for the left gun and mounting the guns at different heights, i.e. definitely very impractical).

            One of the first uses of the M. 38 was to replace the dual Mod. 35 Fiat guns in the late production L3/35 (old designation: CV-35) tankettes (officially light tanks). The Bredas were more reliable and more compact, which allowed for greater traverse in the dual flexible mount (this of course did not save the L3/35 from obsolescence against the much more formidable British Mk. VI light tanks).

          • “reducing firing gas infiltration into the fighting compartment”
            But this make little sense, as most Italian tanks of World War II era have twin-linked Breda Mod. 38. For me it looks as very go-around problem solution, rather than designing bigger-capacity magazine or belt-fed.
            I am aware of following Italian tanks and armored vehicles using twin Breda Mod. 38:
            Carro Veloce CV-35 – in hull
            Fiat M11/39 – in turret
            Fiat M13/40 – in hull
            Fiat M14/41 – in hull
            Carro Armato M15/42 – in hull
            Why did they prefer twin machine gun, rather than one with bigger capacity?

          • “requires a higher reload speed against swarming enemy infantry”
            Tanks rarely fight alone, smallest units (at least in Soviet Union during Great Patriotic War) was 3 tanks.

            Now I found, that Japanese used tank machine gun with even smaller capacity – Type 97 holding only 20.

          • “One more thing to consider is that the M. 38 was often used in double mounts, which would have made strip feed even more difficult to manage (not strictly impossible, but it would have required left handed feed for the left gun and mounting the guns at different heights, i.e. definitely very impractical).”
            I think that if you remove 1 machine gun from twin, that one which remain might be equipped with big-capacity magazine, for example French Reibel has capacity 150:
            and was used in (cramped-turreted) tanks of Armée de Terre like for example Hotchkiss H35

          • I have wondered about the twin mount as well, but I have never found any explanation in any source I have encountered. Possibly it was to give higher rate of fire in critical situations. It would make sense for the M13, M14 and M15 hull mounts, since hull ball mounts were essentially “spray and pray” anyways, due to poor visibility, but of course that does not explain the earlier L3/35 and M11 mounts. Twin mount would also increase reliability, which could have been thought critical for the L3, since it had no other mounted weapons in basic configuration.

            It must be noted that on the L3 the Mod. 38 replaced the Mod. 35, which was also on twin mount, even though it fed from 50 round belts. The Mod. 35 also had a higher theoretical rate of fire, although in practice the 600 rpm setting was rarely used after they were fitted with a decelerator and fire rate selector. (It would lead to ammo cook-offs and failures to extract, although the latter could be avoided by keeping the chamber and ammunition really well oiled — not easy to do under field conditions)

          • On the various “ouvrages” of the Maginot line and similar French defensive works, twin machine guns were fired one at a time. The reason for two Hotchkiss or two Reible M31 MGs was so that one could cool while the other was in use. So the gunners would switch between the two.

            Don’t know if that is how Italian tanks did it or not…

          • @Dave: that is certainly one plausible reason for using twin mounts. It could be any, or perhaps all of the reasons mentioned together. Still, I don’t see much need for long sustained fire or exceptional reliability on the hull mounts of the M13, M14 and M15. It also seems to have been a rather unique solution; I can’t think of any other tanks with twin hull machine gun mounts.

          • “I can’t think of any other tanks with twin hull machine gun mounts.”
            U.S. made M6 Heavy Tank has twin machine gun in hull
            TM 9-721
            WAR DEPARTMENT
            HEAVY TANKS
            M6 AND M6A1
            FEBRUARY 5, 1943
            states that:
            5. DATA
            c. Armament.
            GUN, machine, cal. 50, M2, HB (twin mount T-52), in bow of hull

    • During WWI the Italians used both the Vivien Bessiere than the Bomba Bertone, that used the same “pass through” system.
      The real problem of this kind of grenades, was that not always the projectile passed through the channel.

  7. Just a thought but Italian hand grenades in the western desert campaign were thought by the British at least to be underpowered in terms of explosive mass (or type of explosive in a couple of cases IIRC).

    To the point that some of them were originally thought to be training grenades (red painted small concussion type again from memory).

    Another pointer to the accuracy problems exacercebating the grenade power problem.

    • One of those, the OTO modelo 35 grenade;

      Had a nasty habit of not fully arming its “all ways” impact fuze if it was thrown less than about 20 meters. However, if it were disturbed in any way after landing, even several days later, it would detonate. The SRCM and Breda M35 grenades, which used variants of the same impact detonator, were similarly contrary.

      When British troops in the Western desert campaign referred to Italian hand grenades as “Red Devils”, it wasn’t just because they were painted that color.



    • The explosive filling of the SRCM 35 hand grenade was of 43g TNT, that of the Breda 35 of 63g. For a comparison, a US MKII hand grenade, post 1944, was filled with 52G TNT. The italian bombs were designed so that the splinters were of small dimensions, so they were lethal in a smaller radius in respect to the “pineapple” models, but whith the pattern being more uniform around the point of explosion (pineapple bombs tend to fragment in few pieces, so they hit at random. They could kill someone distant from the explosion, and spare someone close to it).
      The British used the Mills bomb, that was filled with 71g of TNT mixture, but that was dangerous for the thrower too.
      The SRCM grenade had been used by the Italian Army until very recently, in Afghanistan too.

  8. In addition to the previous manuals, this is the one with the charateristics of the SR2 grenade.

    The bomb was filled with 32gr of TNT, into an iron case, and with an iron spiral around it to ensure fragmentation. It couldn’t be fired closer to 50m for the safety of the shooter.
    The three positions of the grenade sights were for 130m, 190m and 230m. The grenade could be launched up to 450m shooting at higher angles.

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