What is the role of the bolt carrier assembly in the M16A3/M4A1 service rifle?

The bolt carrier assembly plays a crucial role in the functioning of the M16A3/M4A1 service rifle, as it is responsible for ejecting spent cartridges and chambering new rounds. When the rifle is fired, the bolt carrier moves rearward due to the gas operating system, which allows the spent cartridge case to be ejected from the chamber. As the bolt carrier returns forward, it strips a new round from the magazine and chambers it into the barrel, preparing the rifle for the next shot. This cycling of the bolt carrier is essential for the semi-automatic or automatic operation of the rifle, ensuring continuous firing and effective operation in various scenarios. Without this function, the rifle would not be able to fire multiple rounds efficiently.