Breda M37

The Mitragliatrice Breda calibro 8 modello 37 (commonly known as the Breda mod. 37 or simply Breda 37) was an Italian Medium machine gun produced by Breda and adopted in 1937 by the Royal Italian Army. It was the standard machine gun for the Royal Italian Army during World War II, and continued to be used by the Italian Army after the conflict. The Breda 37 was meant as company/battalion support as compared to the more troublesome Breda 30 meant for squad/platoon support, and proved far more effective in combat, though possessing some of the same problematic features of the Breda 30.
Design and operation.
The Breda M37 was a gas-operated, air-cooled medium machine gun. The Breda used a slightly larger cartridge than its rivals, the 8x59mm RB Breda. A common misnomer, the Breda 37 does contain a camming mechanism for initial extraction of the cartridge case after firing, which means that each cartridge does not to be oiled before being fed into the chamber. There is no provision for a oiler on any variant of the Breda 37, unlike its predecessor, the Breda 30 in 6.5mm carcano.
Another drawback was that the gun was fed by 20-round trays of cartridges. This limited continuous fire, as the gun could be fired rapidly only when a second crew member fed in one ammunition tray after another (although being air cooled the gun would be unable to fire more than short bursts anyway, or it would rapidly overheat). Another peculiarity of the design is that the spent cases were reinserted in the tray as each round was fired. The mechanical energy required to perform this function substantially reduced the rate of fire, and the weapon tended to jam whenever a case was reinserted even slightly out of line. It also meant that, in the event the metal clips had to be reused, the gunner's assistant first had to remove the empty cases from the trays. Although, this is a non-issue as the feed tray loading machine removes the empty cases from the trays as it refills them with fresh ammunition.
This design flaw was actually intentional. Recycling cartridge cases for reloading was a common practice in some militaries of the time (admonitions to collect and clean spent cartridges are found on ammunition carton labels). The trays were supposed to be returned with the spent cartridges still inside to ammo supply points. There the trays would be emptied and reloaded and the spent cartridges were reboxed and repacked for reloading. The realities of combat made this idea impractical.
Service use.
In service, the Breda 37 and 38 proved to be fairly reliable medium machine guns. Perhaps because the heavy support weapons received more attention from their crews, field reports were generally positive except for jams caused by desert sand and dust, which in the Western Desert affected all infantry machine guns to some extent. The Breda 37's slow rate of fire helped prevent overheating during prolonged fire, and its powerful, heavy-bullet cartridge had excellent range and penetration. Still, this machine gun was almost twice as heavy as the German machine guns and heavier than weapons like the M1919. In fact, it was the heaviest World War II rifle-caliber machine gun, and unnecessarily complex to use and deploy. This was another issue for Italians, whose mobility was limited by their weak truck fleet. The tripod added around 20 kg to the complex, putting it at around 40 kilograms.
The M37 was also adopted by the Portuguese armed forces, who placed it into service as the Metralhadora pesada 7,92 mm m/938 Breda heavy machine gun. The Breda saw extensive service in Portugal's African colonies during the early stages of the Portuguese Colonial Wars. 
The Breda Modello 38 was intended for vehicle use, and was fed from a top-mounted box magazine. The Modello 38 used a pistol style grip, rather than the twin firing handles of the Modello 37. This was the main vehicle-mounted machine gun used in fighting vehicles by the Royal Italian Army.
Production ended in 1943. It was still used as a standard machine gun after the war, until it was replaced by more modern machine guns.