[3] 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.

The trays were supposed to be returned with the spent cartridges still inside to ammo supply points.

[3] In fact, it was the heaviest World War II rifle-caliber machine gun, and unnecessarily complex to use and deploy.

In Regia Marina service, the M37 was used aboard vessels from aviso scorta (destroyer escort/torpedo boat) rank, such as the 840-ton Orsa class which carried two per ship as tertiary gun armament, down to small flotilla craft.

Likewise, the early examples of the VAS anti-submarine launch (Vedetta Antisommergibile) carried a pair of M37s forward in place of the designed 20mm gun, owing to production shortages of the heavier weapon.

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.

This was the main vehicle-mounted machine gun used in fighting vehicles by the Royal Italian Army.