What are the two major components of the M16 and M4 weapons?

The upper receiver and the lower receiver are the primary components of the M16 and M4 rifles, which work together to form the core structure of the weapon. The upper receiver houses critical components such as the bolt carrier group, barrel, and sights, while the lower receiver contains the trigger mechanism, magazine well, and stock attachment point. This separation into two receivers allows for easier maintenance, modifications, and replacements.

In the context of rifle operation, the upper and lower receivers can be independently interchanged, meaning that if one part is damaged or requires upgrading, the other can remain intact. This modular design also enhances the versatility of the M16 and M4, enabling soldiers to adapt their weapons to various missions and user preferences.

The other choices lack the significance of being the two major components that structure the functioning and form of these weapons, focusing instead on ancillary components or features that do not represent the core assembly of the rifles.