The M240B is classified as a _______________ bolt weapon.

The M240B is classified as an open bolt weapon, which means that the bolt is in the rear position when the weapon is not firing. When the trigger is pulled, the bolt moves forward to chamber a round and then immediately begins its rearward motion after firing, which allows for a cooling effect and reduces the risk of a cook-off under certain conditions. This open bolt design is beneficial in mitigating issues related to heat buildup, especially during sustained firing, as it keeps the chamber cooler when not in use.

In contrast, closed bolt systems have the bolt forward and the chamber sealed until the trigger is pulled, which can sometimes lead to higher temperatures in the chamber area. Thus, understanding the operational principle of open bolt mechanisms is essential because they offer specific advantages, particularly in machine guns like the M240B, which are designed for high-volume fire scenarios.