Which feature helps prevent the Mk19 from cooking off?

The feature that helps prevent the Mk19 from cooking off is its air-cooled design. Cooking off can occur when the temperature in a firearm becomes high enough to ignite the propellant in a chambered round without the trigger being pulled. An air-cooled design, which facilitates heat dissipation by allowing air to circulate around the barrel, is crucial in managing temperatures during sustained fire. This cooling method helps maintain safe operational temperatures, reducing the likelihood of a chambered round igniting from excessive heat.

While other features like the gas-operated action and open bolt configuration play important roles in the overall functioning of the firearm, they do not directly address the issue of preventing cooking off in the same way that an effective cooling system does. The open bolt configuration, for example, can also assist in cooling by allowing airflow into the chamber area, but it is the air-cooled design specifically that is instrumental in maintaining lower temperatures to avert cooking off incidents.