Sorry, my error. The internal safety shoulders are intended to keep the rifle from firing with the bolt unlocked if the firing pin breaks. Ordinarily, the cocking cam prevents the cocking piece and firing pin from going forward if the bolt is not fully locked. But the flaw in the design is that if the firing pin breaks, the cocking piece cannot stop the firing pin from moving forward and firing a round being held by the extractor.
Olson (Page 96) says, "Safety firing pin ... has lugs that align with shoulders in the bolt when the action is unlocked. According to German patents, this feature prevents firing if firing pin should break when the bolt is open."
Jim