What is a critical safety procedure when handling the weapon in Condition 4?

When handling the M9 service pistol in Condition 4, which indicates that the weapon is entirely unloaded, ensuring that no ammunition is present is an essential safety procedure. This condition means that the magazine is removed, and the chamber is empty. Checking that there is no ammunition present helps to prevent accidental discharges and promotes a safe handling environment, particularly when the firearm is being handled by those who may not be familiar with it or in training scenarios. Adhering to this safety measure reinforces proper gun safety protocols, preventing mishaps that could lead to injury or unintended consequences.

The other options involve actions that could compromise safety. Ensuring the weapon is still loaded contradicts the principles of Condition 4, which relies on the firearm being unloaded. Preparing to engage a threat implies readiness to use the weapon, which is inappropriate when the firearm is in a condition lacking ammunition. Loading the weapon for practice should only occur when it's confirmed to be safe and in a condition to do so, which is not aligned with the safety protocol required in Condition 4. Therefore, confirming that no ammunition is present is the best practice in this context.