Which of the following is NOT part of the M4 immediate action sequence POPS?

The immediate action sequence "POPS" for the M4 involves critical steps to quickly address malfunctions with the weapon. Each component of this acronym serves a specific purpose in responding to a failure to fire situation. The process includes pulling the charging handle to ensure there is a round chambered, observing the round to understand whether it has fired or any issues are present, tapping the magazine to ensure it is properly seated, and squeezing the trigger to fire if the problem has been resolved.

The part that is not included in this immediate action sequence is tapping the magazine. While ensuring the magazine is properly seated is an essential part of weapon readiness, it does not form a specific step in the POPS immediate action sequence itself. The POPS framework focuses more broadly on addressing the action of the weapon rather than adjustments to the magazine. Therefore, the reason tapping the magazine is identified as not part of the POPS sequence lies in its absence from the specific steps outlined in the immediate action protocol for the M4.