The Breda PG ("Presa Gas" - Gas Operated) was developed by Sestilio Fiorini in 1931 and put into production at Breda's factory in Rome. It was offered as a weapon for commercial sale and export, as well as being one of the several entrants in Italy's semiautomatic rifle trials in the late 1930s. Unlike most of the other competitors in that trial, the Breda PG did actually find a commercial buyer (albeit a small one).
The government of Costa Rica purchased 800 PG rifles. These were designated Moschetto Automatico, as they were equipped with a 4-round burst option as well as semiautomatic They fired from an open bolt (in both semiauto and burst modes) and were chambered for the 7x57mm Mauser cartridge, which was a common and popular round in Latin America at the time.
The Italian military trials rifle was somewhat different. In addition to using the standard Italian 6.5x52mm Carcano cartridge, it was semiautomatic only and fired from a closed bolt. These were designated Fucil Semiautomatico, and only a few hundred were made (at most).
Both versions used large detachable box magazines, including 20-, 30- and even 50-round varieties. The Costa Rican version of the gun shows some elements of the coming assault rifle style of firearm, but it's rifle caliber cartridge and open bolt operation (and its awkward handling) prevented it from showcasing the possibilities of that style of firearm.
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