Which safety feature interrupts the forward movement of the hammer during a mechanical failure?

The half cock safety notch is a critical safety feature in the design of the M9 service pistol that interrupts the forward movement of the hammer during a mechanical failure. This safety mechanism serves as a secondary point of engagement for the hammer, ensuring that if a malfunction or failure occurs while the hammer is in a cocked position, the hammer can safely rest in this half cock position rather than falling fully forward.

This feature adds an extra layer of safety by preventing accidental discharge caused by a failure in the trigger or sear mechanism. In other words, if there are issues that might otherwise cause the hammer to fall unintentionally, the half cock position provides a safeguard that mitigates this risk.

The disconnector, while related to the trigger mechanism, serves a different role—ensuring that the firearm only fires when the trigger is pulled fully rearward. The sear is responsible for retaining the hammer until the trigger is pulled, but does not provide the same safety backup as the half cock notch. The trigger bar connects the trigger to the sear, but it does not directly contribute to the hammer safety mechanism.

Therefore, the half cock safety notch specifically prevents the hammer from moving forward in the event of a mechanical failure, making it an essential feature