Which step ensures that the hammer is cocked in the firing position during loading procedures?

Locking the bolt to the rear is a crucial step in loading procedures for the M16A3/M4A1 service rifle, as it ensures that the weapon is in a safe and ready state for loading. When the bolt is locked to the rear, it exposes the chamber for inspection and loading of the magazine. This action not only allows the operator to visually check that the weapon is clear of any obstructions, but also positions the hammer in the cocked state, meaning that it's ready to strike the firing pin once a round is chambered and the trigger is pulled.

Ensuring the magazine is seated, closing the ejection port cover, and placing the selector lever in the safe position, although important steps in the overall process, do not specifically address the cocking of the hammer. The magazine seating is to ensure that ammunition is available, the ejection port cover protects the internal components, and selecting 'safe' is about preventing accidental discharge. However, it is the action of locking the bolt to the rear that directly relates to cocking the hammer and putting the rifle in a state ready for firing.