This study was served as a foundational investigation about Cook-off phenomenon of a 7.62mm caliber machine gun. In this paper, the Cook-off phenomenon was described and the test precedure developed with reference to TOP 3-2-045 was introduced along with the test firearm. Through live-fire tests conducted according to the test procedure, changes in barrel temperature based on the number of rounds fired, as well as the peak temperature, were observed. The occurrence, time and temperature of cook-off were also identified. Lastly, an analysis of the derived test results was conducted, and the limitations of this study were discussed along with suggestions for future studies.