What action must be performed to achieve incomplete locking in the M9 service pistol?

To achieve incomplete locking in the M9 service pistol, factors related to the magazine or ammunition can play a significant role. Incomplete locking generally occurs when the slide doesn't fully lock into place during the cycle of operation, which can commonly be caused by malfunctions associated with the magazine or the ammunition used.

When there is a problem with the magazine—such as it being dirty, damaged, or improperly seated—it can lead to feeding issues that result in the slide not being able to push the round fully into battery. Similarly, using ammunition that is not correctly loaded, either due to manufacturing defects or damage, can also lead to failures in the locking mechanism. These malfunctions interfere with the proper cycling of the pistol, thereby preventing complete locking.

Issues like engaging the safety, improper cleaning, or an incorrect grip may affect the operation of the firearm but do not directly relate to the mechanism of locking or unlocking in terms of the cycle of firing and can lead to other kinds of malfunctions or handling errors. Thus, focusing on magazine or ammunition-related problems directly addresses the cause of incomplete locking in this context.