Which action must be performed when the slide is assembled in step 1?

When assembling the slide of the M9 service pistol, it is essential to grasp the slide with the bottom facing up. This position ensures that the slide is oriented correctly for further assembly steps, allowing for proper alignment and fit of the various components. Holding the slide this way provides better visibility and accessibility to the areas where other parts will need to be installed, such as the barrel and recoil spring.

This correct method of grasping the slide aids in preventing mishaps during the assembly process, such as misalignment or dropping parts. Each step in the assembly process is designed to ensure functionality and safety, and starting with the correct grip is foundational to achieving that goal. Proper technique is crucial for building muscle memory and ensuring that reassembly is completed efficiently and safely in field situations.