Safety mechanism for blowback firearm

A safety mechanism for a self-loading firearm configured for blowback operation, the safety mechanism comprising:

• a receiver including a cam surface;
• a hammer or striker coupled to the receiver and movable between a cocked position and a fire position;
• a breechblock configured to reciprocate along a top of the receiver between a recoil position and a battery position;
• an actuator on the breechblock, the actuator having an end positioned to engage the cam surface on the receiver when the breechblock is within a predefined distance from the battery position;
• a lever actuatable by the actuator and configured to move from a blocking position to a non-blocking position when the actuator engages the cam surface;
• wherein when the breechblock is out of the battery position by more than the predetermined distance, the actuator is in a first position and the lever is in the blocking position, and when the breechblock is within the predefined distance of the battery position the actuator is in a second position and the lever is in the non-blocking position.