The first prototype was built in 1942 and the ~1,000 built by the FNA-B according to Ian McCollum of Forgotten Weapons (Fabbrica Nazionale d'Armi di Brescia, "Brescia National Arms Factory", hence the name) were issued to German and Italian RSI (Repubblica Sociale Italiana) units fighting in Northern Italy.

Upon firing, the bolt head retracts, and begins to rotate the lever; the base of which is against a lug in the body.

This lever is pivoted to delay the opening movement in order to allow the bullet to leave the barrel.

The base of the lever then pulls clear of the lug, and the whole bolt unit continues to recoil as one piece.

[3] This live firing example was provided with modern 9x19 parabellum ammunition, so it is most likely that the cyclic rate that was see in World War II is slightly lower.