Which situation describes a "cook off" in firearms?

A "cook off" in firearms is specifically defined as ignition caused by barrel heat. This phenomenon occurs when the barrel of a firearm reaches a high temperature due to sustained firing or other factors. If the temperature becomes sufficiently elevated, it can cause a round in the chamber to ignite without the trigger being pulled. This can be particularly dangerous as it can lead to unintended discharges, potentially compromising the safety of the operator and those in proximity.

Understanding this concept is crucial for handling firearms safely, especially in situations where rapid firing occurs, leading to increased barrel heat. Recognizing the conditions that can lead to a cook off helps in implementing preventive measures during training or operational scenarios.