What is the first step when installing the operating assembly?

The correct first step when installing the operating assembly is to push the bolt and operating rod assembly into the receiver. This step is crucial because the proper seating of the bolt and operating rod is essential for the functionality of the operating system within the firearm. The bolt and operating rod must be aligned and engaged correctly with the receiver for the mechanism to work seamlessly during operation.

In firearms, this process is foundational as it sets the stage for subsequent steps, such as securing the assembly and ensuring that everything is properly fitted. Once the assembly is correctly pushed into the receiver, it can be stabilized and further secured using screws and other components.

The other actions listed, such as inserting components or securing them, are dependent on the initial correct installation of the bolt and operating rod assembly. Therefore, the focus on ensuring that this assembly is pushed into place first is key to the overall assembly process of the operating system.