Which one of the following is NOT a characteristic of the M16A2 Service Rifle?

The M16A2 Service Rifle is designed as a lightweight, shoulder-fired weapon primarily for infantry use. Its operation is gas-powered, relying on a gas mechanism to cycle the action after firing a round. In terms of cooling, the M16A2 is air-cooled, meaning it dissipates heat generated during firing through exposure to the air, rather than using a cooling liquid.

Water cooling, as referenced in the selected choice, is not a characteristic of the M16A2. Water-cooled systems are typically found in heavy machine guns or artillery pieces where sustained fire generates a significant amount of heat that needs to be managed differently compared to the rapid-fire capabilities and intent of a service rifle like the M16A2.

Therefore, identifying water cooling as a characteristic of the M16A2 is inaccurate, as the rifle uses an air-cooling method consistent with its design and purpose. Understanding these details is crucial for recognizing the operational features of the weapon within the context of military training and usage.