A firearm has a frame, a trigger, a trigger bar, a hammer-type firing mechanism including a hammer having a hammer pin connected to the trigger via the trigger bar and a firing pin, and an automatic firing pin block safety mechanism (“automatic safety”) including a flange that is spring biased into engagement with the firing pin and a pivot lock arm rotatably mounted to the hammer pin and releasable engageable with the flange. The flange blocks the firing pin from discharging a chambered round unless and until the trigger is positively actuated. The automatic safety reduces the risk of accidental discharge, thereby rendering the firearm safer.