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Reibel machine gun
Reibel machine gun
Reibel machine gun
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A Jumelage de mitrailleuses Reibel twin-mounting for use in fortifications. Shown without guns mounted, front oblique angle. Note heavy metal protective shrouding for the barrels, and circular openings for pan magazines. Square frame is intended to bolt into standard embrasures.

Key Information

The MAC mle 1931 machine gun (official French designation Mitrailleuse modèle 1931 - machine gun, model of 1931), was a machine gun used in French tanks of the World War II era, as well as in fortifications such as the Maginot line. It is also sometimes known as the JM Reibel, from Jumelage de mitrailleuses, or Reibel twin-mounted guns and really refers to the specialized twin-mounting frame used in JM cloche cupolas on the Maginot Line fortifications, while MAC mle 1931 refers specifically to the gun. The JM twin-mounts were the standard emplacement for the mle 1931 in fixed fortifications, while tanks and other AFVs received single guns.

Overview

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Opposite side of Reibel/MAC 1931 machine gun on display at Israel Defense Forces History Museum

The Reibel machine gun is a gas operated weapon chambered in the 7.5 mm MAS cartridge and was loaded with vertical, side-mounted, 150-round pan magazines. The variant used in fortifications was modified with a different rifling to accommodate the balle D heavy ball type of ammunition.

Some other guns in French service during the late 1940s were converted to ground role, with adoption of the side-mounted 35-round box magazines and adapters for US M2 tripods.[citation needed]

The modele 1931 machine gun is a gas operated weapon which fires from open bolt and in full automatic only. It is derived from the French FM 24/29 Fusil-Mitrailleur (light machine gun) also designed by Lt Colonel Reibel, and based on the Browning Automatic Rifle. The FM 24/29 was developed into a heavier machine gun capable of relatively sustained fire, by giving it an extremely thick and massive barrel, to act as a heat sink. This was necessary, since the FM 24/29 lacked a quick-change barrel or water-cooling and its normal light barrel would rapidly overheat and wear out, if fired in more than short bursts, with cooling rests between. The long stroke gas piston is located below the barrel and operates the vertically tilting bolt group. Ammunition is fed from side-mounted multi-layer 150-round pan magazines (with bullets pointing to the center of the round magazine). The gun can be modified to take magazines on either the left or right side, to ease magazine changes while mounted in the standard side-by-side JM twin-mount. Ejection is straight down, through the short chute attached to the base of the receiver, which in fortifications, usually led into a longer tube or chute that directed the spent cases into the ditches outside. The gun was fitted with a forward-curved pistol grip to aid control and a standard rifle-style trigger. When mounted in fortifications, the twin-mount included an adjustable twin-shoulder stock, a tubular metal bar that extended from the rear of the mounting frame, which mounted a horizontal crossbar, with shoulder pads on each end. The operator would face the breeches of the guns and place these pads against his shoulders. He would then use his body to control traverse, while his hands would grip the pistols grips to fire one or both guns. Elevation was controlled by a brass crank underneath the weapon. Twin mountings came in T and F configurations; F types used standard triggers and stocks and were used for embrasure mounts in casemates and cupolas, while the T featured a trigger operated by Bowden cable and was intended for remote use in retractable turrets.[citation needed]

The standard for a mle 1931 in fixed emplacements was a JM Reibel twin-mount, complete with telescopic sight, azimuth and level indicators, elevation screw and spent case ejection chutes. It was manned by a crew of eight, including two gunners, two loaders, two assistant loaders (to fetch ammunition and reload pan magazines with a table-mounted reloading machine that took standard 5-round stripper clips), a mechanic to repair any faults or jams, and a commander to direct or coordinate fire. The purpose of pairing the guns was to allow for sustained and rapid fire. During normal use, the two guns would be fired in turn, allowing the other gun time to cool down. When called for, both guns could be fired together, increasing instantaneous rate of fire. Charts were posted on the walls in each emplacement, outlining standard operating technique:

  • normal fire was 150 rounds (one magazine) per minute, alternating between guns. Each gun would be fired for one minute, in bursts, until the magazine was empty. Then, the gunner would stop, and fire the second gun for a minute while the first gun cooled and was reloaded. Then the first gun could be used again. This rate of fire could be sustained for 3 minutes per gun, before the accumulated heat built to a dangerous level.
  • Accelerated rate was 450 rounds per minute (3 magazines) per gun and was achieved in the same way as normal fire; the gunner would fire off three magazines within a minute and then stop before his barrel overheated, and then repeat with the second. Due to the higher rate of fire, accelerated fire was limited to a maximum of two minutes per gun, since the guns would be so heated after firing 6 magazines each, they would be ready to overheat, even with a minute to cool down after the first 3 magazines.
  • Rapid fire; In cases of emergency, such as enemy crossing the barbed wire, the gunners were authorized to rapid-fire bursts of 75 rounds per gun, either in turn or simultaneously, allowing a full magazines worth to be fired in much less than a minute. Such a rapid rate would very quickly overheat the barrel if not limited to only 75 rounds. To help cool the guns down faster, buckets of water and water sprayers were kept next to each JM emplacement. Barrels were cooled either by spraying them with water (evaporative) or by removing the gun from the mount and dipping the barrel into the water bucket. Up to 20 liters of water could be used per day per emplacement just to cool the barrels.

The JM mount consisted of a thick, metal, square frame, sized to fit into a standard French fortification embrasure (opening); the guns were mounted on an equally heavy-duty pivoting cradle inside this frame. The square frame fitted snugly into the embrasure and was attached by hinges and bolts. This ensured that there were no gaps where enemy bullets could enter into the bunker (except the very small opening that the telescopic sight peeped through), yet allowed the guns to be aimed and trained on anyone outside the walls. Emplacements were often shared with an anti-tank gun sharing the same embrasure opening; the JM mount would be hinged back, and the anti-tank gun slid forward on its ceiling-mounted rail, until its barrel was outside and breech inside. It was surrounded by a similar square frame, which fitted tightly into the embrasure. The only time the occupants of the bunker were exposed to enemy fire, was in the brief moments when switching the machine gun mounting for an artillery mount.[2]

Users

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Non state groups

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See also

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  • FM-24/29, the BAR-based box-magazine fed LMG that the mle 1931 was based on
  • MAC 1934, a faster-firing, belt-fed derivative of the mle 1931 used aboard aircraft

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Reibel machine gun

View on Grokipedia
from Grokipedia
The Reibel machine gun, officially designated the Mitrailleuse modèle 1931 (Mle 1931), was a French gas-operated, full-automatic medium machine gun introduced in 1931 as a coaxial and vehicle-mounted weapon derived from the earlier Chatellerault FM 24/29 light machine gun. Designed by Lieutenant Colonel Reibel to provide sustained suppressive fire in armored and fortified positions, often mounted in twin configuration as the JM Reibel for coaxial use, it chambered the 7.5×54mm French cartridge and utilized a distinctive 150-round drum magazine for high-capacity feeding. With a heavy barrel to dissipate heat during prolonged bursts, it achieved a cyclic rate of fire of approximately 750 rounds per minute (practical rate around 450 rpm), a muzzle velocity of around 820 m/s, and an effective range up to 1,200 meters, making it a key secondary armament in French military doctrine during the interwar period. Developed at the Manufacture d'Armes de (MAC) as part of France's modernization efforts following , the Reibel addressed the need for a reliable, vehicle-adapted automatic weapon capable of mounting in tanks without a traditional stock or sights, emphasizing durability in confined spaces. Variants included the Mle 1931C for tanks, the Mle 1931F for fixed fortifications like the , and the Mle 1934A for aircraft, with overall dimensions measuring about 1.03–1.05 meters in length and a weight of 11.8–18.5 kg depending on the configuration. It fired from an using a long-stroke gas mechanism, ensuring consistent performance under the vibrations of armored vehicles such as the Renault FT-17, , Somua S35, and tanks. During , the Reibel saw widespread deployment in the French Army's armored divisions and defensive networks until the 1940 Fall of France, after which captured examples were redesignated by German forces as the 7.5 mm Kampwagen-Maschinengewehr 311(f) and integrated into occupation units, vehicles, and bunkers. Post-war, surplus stocks continued in service with French colonial forces during conflicts like the Indochina War and , as well as exported or repurposed in nations including (rechambered for ) and during its civil war into the 1970s. Its robust construction and adaptability contributed to its longevity, though it was eventually phased out in favor of more modern designs like the AA-52 by the late .

Development and production

Origins and design influences

The development of the Reibel machine gun was initiated in 1931 at the (MAC) under the direction of Jean Frédéric Jules Reibel, who had previously led the design of the . This effort aimed to produce a more robust variant suited for specialized military roles, building directly on Reibel's earlier work with assistance from Chief Armorer Chosse. The Reibel drew its core design from the FM 24/29, which incorporated principles from the American Browning Automatic Rifle (BAR) to emphasize reliability and controllability in automatic fire. Unlike the infantry-focused FM 24/29, the Reibel was engineered as a coaxial or fixed vehicle-mounted weapon, primarily for French tanks and fortifications, to meet the growing demand for a dependable 7.5 mm automatic gun in armored and defensive applications. This adaptation addressed limitations in existing French small arms, such as the problematic Chauchat from World War I, by prioritizing sustained operation in confined environments. Initial prototypes underwent testing and refinements between 1931 and 1932, focusing on modifying the long-stroke gas-operated system inherited from the FM 24/29 to enable continuous fire without excessive heat buildup or mechanical stress in enclosed spaces like turrets or mounts. These trials ensured the weapon's suitability for high-volume suppressive roles, marking a shift toward integrated support in French .

Manufacturing and adoption

The Reibel machine gun, officially designated the Mitrailleuse MAC modèle 1931, was produced exclusively at the Manufacture d'Armes de (MAC) facilities in , with manufacturing commencing in 1931 following its design as a heavy variant of the earlier MAC modèle 1924/29 . Production ramped up steadily, reaching its peak in the late to meet growing demands for armored vehicle armaments and defensive fortifications. By 1940, a significant number of units had been completed, with the majority allocated to equip French tanks and the extensive network of bunkers and casemates. The weapon's primary role was as a or secondary armament in vehicles, reflecting its robust construction for sustained fire in enclosed mounts. The formally adopted the Reibel in 1931 as the standard machine gun for medium and light tanks, including the and Somua S35, where it provided close-range defensive fire alongside the main armament. Designed under the supervision of Lieutenant Colonel Jean Frédéric Jules Reibel at MAC, it quickly became integral to France's mechanized forces and static defenses. Production faced significant challenges in the late , including bureaucratic delays from overly rigorous inspectorates and broader material shortages amid economic pressures and rearmament efforts leading into . These issues hampered output scaling, though the MAC arsenal managed to sustain deliveries for key strategic priorities like the .

Technical design

Operating system and features

The Reibel machine gun operates using a long-stroke gas system, where gases are tapped from the barrel to drive a located beneath it, which in turn cycles the bolt carrier group rearward to extract and eject the spent cartridge case before chambering a new round. This mechanism employs a vertically that locks into recesses in the receiver walls, ensuring reliable operation under the stresses of sustained fire in enclosed environments. The weapon fires exclusively from an in full-automatic mode only, with the bolt held rearward until the trigger is pulled, enhancing safety by preventing accidental discharge from a . Designed primarily for integration into armored vehicles and fortifications, the Reibel features fixed mountings that allow for synchronization with main armaments, enabling precise alignment for anti-infantry support alongside the primary gun. To accommodate confined crew spaces, it incorporates downward ejection through a short integrated chute at the base of the receiver, often extended with additional tubing in installations to direct spent casings away from the operator and prevent jams or hazards. Optional telescopic sights could be fitted to the mounting assembly for improved accuracy in fixed or turreted applications, though the gun itself lacks integral due to its vehicle-centric role. Ammunition is fed via a vertical, side-mounted 150-round pan magazine, which can be configured for left- or right-hand feed depending on the installation, providing sustained fire capability without frequent reloading. In limited ground or dismounted roles, provisions exist for smaller box magazines, though these were less common and reduced overall capacity. Safety features include a manual selector on the receiver to lock the bolt rearward, preventing unintended firing, while the heavy, fixed barrel—derived from the FM 24/29 —serves as a for prolonged bursts without the need for field replacement.

Specifications

The Reibel machine gun, designated as the MAC Modèle 1931, is chambered primarily in the (MAS) cartridge, with certain export variants adapted for the round. Its unloaded mass is 11.8 kg, facilitating mounting in armored vehicles while providing stability for sustained fire. The overall length measures 1,030 mm, including a 600 mm barrel length designed for balanced handling and ballistic performance. The theoretical cyclic rate of fire reaches approximately 450–500 rounds per minute, though practical rates are controlled at 150 rounds per minute for sustained operation. Muzzle velocity achieves 830 m/s when firing standard , contributing to effective penetration and trajectory stability. The effective firing range extends to 600 meters for precise point targets and up to 1,200 meters for area suppression, aligning with its role in vehicular and defensive applications. As a gas-operated , it typically requires 1-2 operators for vehicle-mounted use, but fortified twin installations may involve up to 8 personnel for loading, maintenance, and operation. is fed from a 150-round pan magazine (149 usable rounds due to a ).

Variants

MAC mle 1931

The Mitrailleuse Châtellerault Modèle 1931 (MAC mle 1931), commonly known as the Reibel machine gun, represented the foundational single-gun configuration of the series, optimized for installation as a in armored vehicles. Developed by the French state at , it evolved from the earlier MAC Mle 1924/29 to meet the demands of vehicular mounting, emphasizing reliability in confined spaces and integration with armaments. Primarily employed in a coaxial role alongside the main tank cannon, the MAC mle 1931 equipped key French interwar and World War II-era vehicles, including the , Hotchkiss H39 , and medium tank. In these applications, it provided against and light targets, enhancing the vehicle's overall combat effectiveness during maneuvers. Variant-specific adaptations focused on seamless turret integration, featuring a compact overall length of 1,030 mm and weight of 11.8 kg to fit within narrow armored housings, along with the omission of a traditional buttstock and open sights to allow direct linkage to the tank's optical fire control systems. The design incorporated adjustable feed and ejection mechanisms, including a downward-ejecting and reversible 150-round pan magazine for left- or right-side installation, ensuring compatibility with diverse turret layouts. Additionally, mounting provisions enabled gearing to align firing with the main gun's traverse and elevation, promoting precise operation without interference. The MAC mle 1931's gas-operated, open-bolt mechanism, with its long-stroke piston and , supported a cyclic of 750 rounds per minute, with practical sustained rates of 150–450 rounds per minute depending on mode, using the cartridge, while a heavy fixed barrel mitigated overheating during prolonged engagements—characteristics aligning with the core Reibel specifications for vehicular use. Production centered on this model as the dominant variant, handled exclusively by the Manufacture d'Armes de from its introduction in 1931 through the fall of in 1940, with output continuing under German oversight into 1942 to supply captured equipment.

JM Reibel

The Jumelage de mitrailleuses Reibel (JM Reibel) was the official designation for a twin-mounted configuration of the Reibel machine gun, introduced in as a specialized defensive weapon system for French fortifications. This setup paired two 7.5 mm MAC mle 1931 Reibel machine guns on a single mount, enabling sustained while allowing one gun to cool during the other's operation. Designed specifically for static defense, the JM Reibel emphasized reliability in prolonged engagements, with each gun fed from a 150-round pan magazine to maintain high-volume output without frequent interruptions. The primary role of the JM Reibel was to equip bunkers and pillboxes along the , where the twin-gun arrangement provided overlapping to cover approaches and enfilade positions effectively against assaults. Installed in combat blocks, casemates, and cupolas, it served as a cornerstone of close-in anti-personnel defense, often integrated into mixed-weapon embrasures alongside anti-tank guns for layered protection. The system's horizontal spanned up to 72 degrees, with a practical of 1,200 meters, making it ideal for denying enemy advances in fortified sectors facing . Unique features of the JM Reibel included electrically synchronized firing mechanisms that alternated between the two guns to prevent overheating, ensuring continuous operation at rates up to 450 rounds per minute per gun. It incorporated and indicators for precise aiming, along with shared telescopic sights that allowed a single gunner to control both weapons effectively. Operated by a of eight—including two gunners, two loaders, two assistant loaders, a , and a —the system was optimized for coordinated defensive actions within confined fortress environments. The JM Reibel was fixed in heavy mounts protected by armored shields, with provisions for daily cooling using approximately 20 liters of per gun to support extended defensive engagements lasting up to 24 hours. These installations, such as in JM cloches and retractable turrets, were connected via underground passages in major ouvrages like Hackenberg and Schoenenbourg, enhancing survivability and resupply during sieges. This design prioritized endurance and firepower density, reflecting the Maginot Line's doctrine of immobile, attrition-based warfare.

Mle 1931F

The Mitrailleuse modèle 1931F was a single-gun variant adapted for fixed fortifications, such as those along the . It shared the core design of the MAC mle 1931 but included mounting adaptations for static emplacements, emphasizing durability in defensive positions without vehicular constraints. Specifications were similar to the base model, with a weight of approximately 11.8 kg and length of 1,030 mm, chambered in , and fed by 150-round pan magazines.

Mle 1934A

The Mitrailleuse de Modèle 1934A (Mle 1934A) was an variant of the Reibel, developed for synchronized installation on . It featured a higher cyclic rate of up to 1,200 rounds per minute to suit aerial combat, with modifications for reduced weight and integration with propeller . Primarily used in French Air Force planes during the late 1930s, it was less common than ground variants.

Operational history

World War II service

The Reibel machine gun saw its primary combat deployment with French armored units during the from May to June 1940. Mounted as the coaxial secondary armament in light and medium tanks, including the medium tank and light tank, it provided against German infantry advances and supported the main gun in engagements against early-war Panzers such as the and . In key battles like Hannut and Montcornet, Reibel-equipped French tanks achieved local tactical successes by leveraging their mobility and firepower to disrupt German breakthroughs, though overall French armored operations were hampered by doctrinal and logistical shortcomings. While reliable for short bursts in tank-to-tank and anti-infantry roles, the Reibel exhibited performance limitations during sustained engagements characteristic of the rapid . Its side-mounted 150-round restricted continuous fire, leading to frequent overheating of the barrel after one or two magazines and increased risk of jamming from feed mechanism stress, which reduced its effectiveness in prolonged fights against massed German assaults. These issues were exacerbated by the gun's gas-operated and the confined conditions inside French tanks, where quick reloading was challenging. Following the French surrender in , large numbers of Reibel machine guns were captured by German forces and redesignated as the 7.5 mm KpfwMG 311(f). The repurposed them for static defenses in occupied , particularly along the Atlantic Wall, where they were adapted with bipods and stocks for and anti-aircraft use by garrison troops. Production of the weapon continued under German occupation at the Châtellerault factory until at least 1942 to meet demand for these secondary roles. Some Reibel machine guns remained in limited service with French forces in and until the Allied landings in 1942-1944, arming retained armored vehicles in defensive roles. Free French units, including those under General Leclerc, also employed captured or stockpiled examples in late-war campaigns, such as the in August 1944, though they were increasingly supplemented by Allied-supplied weapons.

Post-war conflicts

Following the end of , the Reibel machine gun continued to see service in French colonial conflicts, particularly mounted in older armored vehicles or adapted for ground use with tripods for defensive positions and support. In the (1946–1954), French forces employed the MAC 31 variant in chenillettes and H-39 light tanks, with examples operating in early in the conflict and reinforcements arriving from in 1947–1948. The weapon's reliability in tropical conditions made it suitable for both vehicular and dismounted roles, including on riverine patrol boats equipped with twin Reibel mounts for anti-guerrilla operations along waterways. During the (1954–1962), the Reibel armed EBR wheeled armored cars and light tanks, with up to three MAC 31 E guns per vehicle in operations such as the 1956 Bessombourg engagement; units also utilized tripod-mounted versions for fixed defenses against FLN insurgents. Captured or surplus Reibels from French stockpiles extended the weapon's reach to other combatants in post-war conflicts. In the 1948 Arab-Israeli War, Israeli forces acquired ten Hotchkiss H-39 light tanks, each armed with a 7.5 mm Reibel machine gun alongside the main 37 mm SA 38 cannon; these saw combat in Operation Danny near in July 1948, though mechanical issues limited their effectiveness before retirement from frontline service by October. During the (1955–1975), and North Vietnamese forces employed captured Reibels, such as the MAC 31 variant documented in their hands during the Battle of Điện Biên Phủ (1954) and later operations on the Ca Mau Peninsula, providing sustained from French colonial-era supplies. In African decolonization struggles, surplus French Reibels circulated among former colonial militaries and insurgents during the 1960s-1970s. By the 1960s, the Reibel was largely phased out in favor of 7.5 mm or 7.62 mm NATO-standard guns like the AA-52, as French forces modernized inventories and retired associated vehicles such as the EBR and ; remaining stocks lingered in African allies until the 1970s or early 1980s.

Users

State military users

The Reibel machine gun, officially designated as the Mitrailleuse MAC modèle 1931, was primarily adopted by the in 1931 as a and secondary armament for tanks and a defensive weapon in fortifications such as the . It served extensively in the , colonial forces, and air force variants through and into the 1960s. Following the German conquest of in 1940, the captured large numbers of Reibel machine guns for continued service until 1945. German authorities even resumed production of the weapon at the factory until at least 1942, primarily to bolster defenses along the Atlantic Wall. Post-World War II surplus Reibel machine guns were acquired by the Israel Defense Forces (IDF) and used post-WWII, including in vehicles during the 1948 Arab-Israeli War. The North Vietnamese Army inherited stocks of Reibel machine guns from French colonial forces during the First Indochina War and integrated them into their arsenal, using the weapon through the 1970s in both defensive and offensive operations. The Chadian National Army (Armée Nationale Tchadienne) utilized dismounted Reibel machine guns as defensive support weapons during the Chadian Civil War from 1965 to 1979. Switzerland acquired examples, rechambered for , and used them on vehicles such as the Renault R35.

Non-state groups

The employed captured French MAC mle 1931 Reibel machine guns during the .

References

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  2. https://www.forgottenweapons.com/swiss-reibel-m31-tank-fortress-machine-gun/
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  18. https://pdhonline.com/courses/c799/c799handout.pdf
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  20. https://www.maginot.org/armes/armes15_gb.htm
  21. https://tank-afv.com/ww2/france/Somua_S35.php
  22. http://armesfrancaises.free.fr/Mitr%20MAC%2031%20type%20C%20et%20E.html
  23. http://indochine54.free.fr/cefeo/afvs.html
  24. https://lumcelgun.wordpress.com/2017/03/13/la-mitrailleuse-reibel/
  25. https://tanks-encyclopedia.com/hotchkiss-h39-in-israeli-service/
  26. https://www.thearmorylife.com/heavy-weapons-of-the-viet-cong/
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