Which of the following is NOT a characteristic of the M240?

The M240 is known for its specific operational characteristics, and one of the defining features is its cooling method. It operates as an air-cooled machine gun, meaning it relies on the flow of air to dissipate heat generated during firing, rather than using any liquid coolant. This design is advantageous as it allows for versatility and ease of use in various environments without needing a separate water supply.

In contrast, water-cooled systems involve additional components that are generally heavier and require maintenance associated with the water element. Since the M240 does not utilize water for cooling, it clearly separates itself from water-cooled machine guns, making the identification of this feature as NOT characteristic of the M240 straightforward.

The other characteristics—gas operation and being belt-fed—align with the operational design of the M240, making them integral to its functionality in military applications. This context helps to solidify the understanding of the M240's operational mechanics and its cooling system.