Which of the following is part of the cycle of ejecting in the M4 series?

The correct choice in this context is related to the cycle of ejection in the M4 series, focusing on how spent cartridges are removed from the chamber to prepare for the next round. The expulsion of the cartridge is crucial to ensure that the firearm can function correctly and reliably. This action occurs after the firing sequence, where the spent cartridge must be ejected to allow the chamber for a new round. This step is a fundamental part of the semi-automatic or automatic cycling process necessary for the weapon's operation.

The other options represent important aspects of firearms mechanics but do not specifically pertain to the ejection cycle. For example, the locking mechanism activation is related to securing the bolt in place during firing and preparing for the next round but does not describe the ejection process. Back pressure release pertains to the gas system of the firearm, which is involved in cycling the action but again, is not exclusively about ejecting spent cartridges. Trigger reset is a process that allows the shooter to fire again, but it does not directly relate to the mechanical process of ejecting a cartridge. Understanding these distinctions helps to clarify the specific actions involved during the firing cycle of the M4 series.