The LF-57 was developed at Franchi in the mid-1950s. It was the first gun to be produced in mass by the company, and also their first product designed for military use. Production of the LF-57 began in 1957 and it was adopted by the Italian Navy in 1962. It also saw numerous sales to Africa during the 1960s. A long-barreled, semi-automatic version known as the Police Model was marketed in the US in 1962, but saw few sales. Production ended in the early 1980s.
The LF-57 was a blowback-operated submachine gun. It was part of a trend of Italian submachine guns in the 1940s and 50s utilizing "¬"-shaped bolts consisting of two sections; a long section housed over the barrel, and a short section that came down into receiver. The short section carried a fixed striker, extractor, and feed horn. The gun featured a grip safety device.
The body of the LF-57 was constructed from stamped steel. It fed from Beretta Model 38 magazines consisting of 10, 20, 30, or 40 rounds.