Gear Up for 2025: Command the USMC Machine Gunnery Challenge and Conquer Your Aim!

The main components of the Mk-19 machine gun include the receiver, feed slide, cover, sear, bolt, and back plate. Each of these parts plays a crucial role in the weapon's operation.

The receiver is the central unit that houses the operating mechanism and connects all components. The feed slide is responsible for transporting ammunition from the belt to the chamber. The cover serves to protect the internal mechanisms and also has a function in the feeding process. The sear is vital for controlling the firing mechanism by engaging with the bolt to release it at the correct time. Finally, the back plate is essential for structural integrity and housing the bolt guide, allowing for proper operation and cycling of the weapon.

In contrast, the other options mention components that are either not specific to the Mk-19 or do not encompass the key operational parts required for its function. For instance, while a barrel is essential for nearly all firearms, it alone does not cover the complexity and specific components of the Mk-19. Components like triggers and magazines are more relevant to different types of firearms and do not represent the distinct assembly and operation of the Mk-19 machine gun.