Safety device for a breechblock of a firearm

Safety device for a breechblock of a firearm for limiting accidental sliding of said breechblock (14) caused by an impact to the firearm, said safety device comprising a locking lever (15) affixed to said breechblock (14), said locking lever (15) being axially pivoted at a front end (16) to structure (17) of the firearm to allow rotation of said locking lever (15) in axis of rotation (11), wherein said front end (16) of said structure (17) is forked to house said lever (15), wherein said locking lever (15) and said front end (16) of the structure have opposed walls (31) with matching cylindrical profiles and abutment elements (32, 33), that define an upper limit position and a lower limit position for the rotation of said locking lever (15),an elastic return element (18) connected to said locking lever (15), for keeping said locking lever (15 in a rest position during conditions of normal use of the firearm, said locking lever (15) being equipped with an engagement element (19) for engagement with a seat (23) of said breechblock (14) and affixed to said breechblock (14) to provide said locking lever (15) with a centre of gravity (G) which is offset with respect to the axis of rotation (11) of said locking lever (15), to cause inertial rotation of said locking lever (15) to cause said locking lever (15) to engage said seat (23) when said firearm is subjected to an impact.