Which component serves as support for all major groups and assemblies of the M500A1 service shotgun?

The receiver group is the central component of the M500A1 service shotgun, serving as the backbone for all major groups and assemblies of the firearm. It houses critical mechanical elements such as the trigger mechanism, bolt, and action, which are essential for the shotgun's operation. Additionally, the receiver group provides the framework that integrates the barrel, stock, and other components, ensuring that they function in unison during firing.

This component is vital for the proper alignment, stability, and performance of the shotgun. It is also where other elements, like the loading mechanism and safety features, are integrated. Without a properly functioning receiver group, the overall performance and reliability of the shotgun would be compromised.