During which step should the slide stop be released to allow the slide to move forward?

The slide stop should be released during the fourth step of the function check. This particular step is crucial because it verifies that the slide, after being locked back, can engage and move forward smoothly when the slide stop is released. This action ensures that the firearm is functioning correctly, allowing the chamber to load a round as intended.

Releasing the slide stop at this moment confirms that the slide moves forward under spring tension, indicating that the internal mechanisms of the pistol are operating correctly. This check is vital for maintaining reliability and ensuring that the weapon can safely and effectively cycle ammunition. In earlier or later steps of the function check, the priorities and actions differ, focusing on other aspects of the firearm's operation rather than the mechanical interaction of the slide and slide stop.