For those of us so blessed to have served with open-bolt machine guns, we know that clearing malfunctions can be a real chore. Where standard shoulder-fired small arms like the M4 are truly difficult to get to cook-off temperatures, belt-fed weapons can get to those short, fast, and in a hurry. In fact, this is the very reason why (including accelerated barrel wear) that most belt-fed weapons have a provision for quick barrel changes.
Most carbine users do not take into account the temperature of the barrel at all. In case of class 4 malfunctions (double feeds), soldiers are taught to immediately start remedial and later rectifying action to clear the issue. However, doing this with a belt-fed can be hazardous to your health in a training environment, as cook-offs are far more likely.
One ISAF soldier learned this the hard way. According to the video posted by SAM K, the hapless soldier was treating a Marine at Camp Leatherneck to some good German MG3 / MG42 action. The weapon malfunctions and the soldier immediately started clearing the malfunction.
While following some solid remedial action, the soldier forgot one thing – that a hot weapon is indeed a dangerous one (pun intended). While doing the correct remedial actions, he forgot to let the weapon cool. By forgetting this critical step, he took a face full of premature detonation.
Fortunately, the cheek scar will be the lesson learned. No other injury was reported.