Which component is NOT part of the M4 major components?

The trigger assembly is not considered one of the major components of the M4 rifle. The M4 is generally broken down into several key components, which primarily include the upper receiver assembly, lower receiver assembly, and magazine assembly. These components are fundamental to the functioning and assembly of the rifle.

The upper receiver assembly houses essential parts such as the bolt carrier group and the barrel, while the lower receiver includes critical controls like the trigger mechanism, safety selector, and magazine well. The magazine assembly, on the other hand, is essential for feeding ammunition into the rifle but is not listed as a major component of the M4 itself.

The trigger assembly, while important for the operation of the firearm, is more of a sub-component within the lower receiver rather than a standalone part that makes up the M4's major components. This distinction emphasizes why it is correctly identified as not being one of the main components of the M4 rifle.