What should be done after grasping the slide and aligning it onto the receiver assembly guide rails?

After grasping the slide and aligning it onto the receiver assembly guide rails, the correct action is to hold until the slide clicks into place. This step is crucial because it ensures that the slide is properly seated and fully engaged with the receiver. The clicking sound is an indication that the slide has locked securely into position, which is essential for the safe and correct functioning of the pistol.

This process is fundamental to ensure that the firearm is assembled correctly before use. If the slide is not held or locked in place, it could lead to malfunctions during firing, such as failures to feed or extract, which can compromise safety and performance. Therefore, being attentive to the clicking sound during reassembly is an important part of the training and operation procedures for the M9 Service Pistol.