The Beretta 38/42 submachine gun. Designed by the talented Italian designer Tullio Marengoni, the 38/42 underwent modifications to expedite wartime production, resulting in a more compact and faster firearm compared to its predecessor, the 1938A model.

The Beretta 38/42 series of submachine guns traces its origins back to the Beretta Model 1918, which was based on the Villar Perosa design. However, Marengoni's 38 series, starting with the prewar 1938A model, truly marked the beginning of a legendary firearm lineage. The early 1938A Berettas rivaled the famous Colt-produced 1921 Thompsons in terms of construction quality, setting a standard for excellence. The 1938A model continued to be manufactured in various variations until as late as 1950, a testament to its enduring effectiveness and design.

As World War II progressed and the demand for weapons increased, Marengoni redesigned the 1938A to allow faster and cheaper production, leading to the creation of the Moschetto Automatico Beretta 38/42 submachine gun, or the MAB 38/42. While this newer model lacked some of the refinements of the previous 1938A, it compensated with enhanced handiness and faster targeting capabilities. The MAB 38/42 featured sheet metal stampings to replace milled steel machined parts, resulting in a lighter, more cost-effective design. The polished blue finish of the 38A was also deemed unnecessary, and the 38/42 models were finished in a dull blue/black.

Functionally, the Beretta subguns utilized the common open bolt/blowback design, with the added convenience of a non-reciprocating cocking knob/dust cover. During firing, the cocking handle remained stationary, enclosed by the dust cover, which kept out debris and minimized the risk of stoppages. Early production runs included a Schmeisser-style bolt-locking safety, but later models incorporated a manual safety on the top cover, providing added safety in both cocked and closed positions.

The 38/42 boasted a simple folding leaf sight calibrated for 100 and 200 meters, paired with an unprotected blade-type front sight. Early models featured a fluted barrel to aid in heat dissipation during extended firing, but this was later replaced with an easier-to-manufacture smooth barrel. Beretta barrels, made from nickel steel and rifled on a broaching machine, featured two compensator slots at the muzzle top. A distinguishing feature of Beretta submachine guns was the dual trigger configuration, with the front trigger controlling semi-automatic fire and the rear trigger enabling full-auto function. The rear trigger was serrated, facilitating easy identification during low visibility situations.

Beretta stocks were typically crafted from dried beech, but some 38/49 and later models could be ordered with walnut stocks. Several prototype models with folding stocks, similar to the German MP40, were designed but not mass-produced. During the war, with the German occupation of the Beretta plant in Northern Italy, the production of 38/42s continued under German supervision, marked with Nazi Waffenamts. The German Army designated them as the MP740(i) and held them in high regard for their accuracy in both full-auto and semi-auto modes.

The Beretta submachine gun's service extended beyond its wartime role, as it continued to be manufactured even after the war ended. Marengoni made slight modifications to the design near the war's end, aiming for post-war export sales. The resulting 38/44 model, introduced in 1945, featured a shorter, lighter bolt and a larger recoil spring that slid over the rear of the bolt, maintaining the same cyclic rate. The 38/44 model's smooth barrel, resembling the late production 38/42 model, ensured optimal performance.

The Beretta submachine guns were lauded for their excellent double feed magazines, which were less prone to jamming, required less spring pressure, and were easy to load. These box-type magazines came in various capacities and were remarkably interchangeable among Italian subguns. The UZI magazine's design was directly inspired by the successful Beretta design, while the U.S. Thompson submachine guns adopted a similar concept. The Beretta magazines, made of heavier gauge metal, proved more durable than their Thompson counterparts. The submachine gun's reliability and magazine compatibility made it highly regarded by various customers, including the German police, Syria, Pakistan, Iran, and Costa Rica.