Reibel machine gun

Lore & Background

The MAC mle 1931 was developed from the FM 24/29 light machine gun, itself based on the Browning Automatic Rifle. To allow sustained fire without a quick-change barrel or water cooling, the barrel was made extremely thick and massive to act as a heat sink. The long-stroke gas piston is below the barrel and operates a vertically tilting bolt. Ammunition is fed from a side-mounted 150-round pan magazine, with bullets pointing toward the center. The gun can be modified to accept magazines on either side to facilitate changes in the twin-mount. Ejection is straight down through a chute, which in fortifications led to a longer tube directing cases outside.

In fixed fortifications, the standard installation was the JM Reibel twin-mount, which held two guns side by side in a heavy metal frame that bolted into a standard embrasure. The operator faced the breeches and used a tubular shoulder stock with pads to control traverse, while hands gripped the pistol grips. Elevation was adjusted with a brass crank. Twin mounts came in F and T configurations: F types used standard triggers for casemates and cupolas, while T types used a Bowden cable trigger for remote use in retractable turrets. The mount included a telescopic sight, azimuth and level indicators, and spent case chutes.

Crews followed posted charts for firing rates. Normal fire alternated guns, each firing 150 rounds per minute for one minute, then cooling while the other fired. Accelerated fire allowed 450 rounds per minute per gun for up to two minutes. In emergencies, rapid fire of 75 rounds per gun could be used, but required water cooling via sprayers or dipping the barrel. The mount could be hinged back to allow an anti-tank gun to slide forward on a ceiling rail, sharing the same embrasure.

Reader's Guide

The Reibel machine gun's significance lies in its role as the primary automatic weapon for French armored vehicles and the Maginot Line fortifications. Its design, derived from the FM 24/29, addressed the need for sustained fire without a quick-change barrel by using a massive barrel as a heat sink, though this limited sustained rates without cooling measures. The twin-mount system allowed alternating fire to manage heat, and the ability to fire both guns simultaneously provided a high instantaneous rate of fire for emergencies. The gun's use in tanks such as the Hotchkiss H35, Renault R35, and AMR 33, as well as on the Renault UE Chenillette, made it a common sight in French armored units. Captured examples were used by German forces as the Kpfw. MG 311(f). After World War II, some guns were converted for ground use with 35-round box magazines and US M2 tripods, and saw service in the Indochina War and the Chadian Civil War. The Reibel's legacy is tied to the defensive doctrine of the Maginot Line and the armored forces of France, and its design influenced the MAC 1934 aircraft machine gun.

Did You Know?

• The gun's barrel was made extremely thick and massive to act as a heat sink, as it lacked a quick-change barrel or water cooling.
• In fixed emplacements, the crew consisted of eight men: two gunners, two loaders, two assistant loaders, a mechanic, and a commander.
• The gun could be modified to accept pan magazines on either the left or right side to ease magazine changes in the twin-mount.