What action starts the extraction and ejection steps during operation?

The action that initiates the extraction and ejection steps of the M9 service pistol operation is unlocking. During the firing sequence, after a round has been fired, the slide begins to move rearward due to the energy released from the fired cartridge. As the slide moves rearward, it must first unlock from the barrel. This unlocking action separates the barrel from the slide, allowing the spent cartridge case to be extracted from the chamber.

Once the barrel is unlocked from the slide, the extractor engages the rim of the cartridge case and pulls it out of the chamber. At this point, the ejector also comes into play, hitting the casing and causing it to flip out of the ejection port. Thus, each of these steps—the unlocking of the barrel and subsequent extraction and ejection—is crucial for the pistol's cycling process. This operation is fundamental to the semi-automatic function of the M9, enabling it to load the next round efficiently after firing.