The Mod. 37 was designed by Tullio Marengoni in 1937 as an updated version of the Beretta Mod. 31 rifle he designed six years prior. The weapon was submitted to the Italian self-loading rifle trials in 1939, where it eventually lost out to the Armaguerra Mod. 39.
One sample of the rifle is currently held in Beretta's reference collection.
The Mod. 37 was a recoil-operated self-loading rifle, and was functionally identical to the Mod. 31 it was based on; operation is very similar to that of the Johnson rifle. However, the Mod. 37 had a few novel changes compared to the Mod. 31. The Mod. 37 had fixed rear sights as opposed to an adjustable one as seen on the Mod. 31.
A very novel addition to the Mod. 37 was the addition of a locking lever located near the front sight; toggling the lever prevents the barrel from recoiling, effectively preventing the rifle from cycling automatically and making it a bolt-action rifle. The barrel recoils within a brass sleeve, similar to the Mod. 31.
The weapon feeds from an internal box magazine, although the actual capacity of the box magazine is unknown; one source claims that the rifle uses a nine-round internal box magazine fed by a special stripper clip, while another claims the rifle uses a ten-round internal box magazine fed by two five-round stripper clips.
The weapon's bolt has six locking lugs. The weapon has a very large firing pin spring, which provides the force to rotate the bolt into battery and serves to prevent slam firing if the bolt was closed by winding the firing pin spring rotationally, allowing it to put direct rotational pressure on the bolt.
Unlocking the bolt is done by a rounded cam surface that the bolt handle stem contacts as the whole barrel and bolt assemble moves backwards; the camming surface will force the bolt handle up and unlock the lugs. Disassembly of the weapon is very simple; engage the safety, push the ejector assembly in, screw off the rear receiver cap and one can pull all the internal components of the weapon out.