I know this thread hasn't been added to for some time, but I am a fireman, in a larger city. I've been to a house fire where rounds were popping off. I wasn't so nervous about the rounds popping off, as I was about the potential of a firearm with a round in the chamber. When we were doing overhaul (clearing the burned stuff out after the fire was out) I did find an AK, with a round in the chamber, and a mag attached.
At the beginning of the video, they do clarify that if a round is in a gun, and it goes off from heat, it'll shoot just like the trigger was pulled, with the same kind of energy out the muzzle. Fortunately, heat rises, and most guns are stored lower in the room if they are kept loaded. (even 1200*F on the ceiling can mean 3-400* 3' off the floor in that room) In our city, we're usually on scene pretty darn fast, and our dept. is known for using aggressive tactics to get the fire put out. This means, that temperatures in a common apartment or single-family home usually don't get hot enough for the ammunition in the chamber to get hot enough to fire off. Also, IF it does get hot enough to fire off the round in an auto-loading rifle, the magazine does NOT have the same thermal insulation capacity as the chamber (thinner metal or plastic), so they would most likely pop off, and render the clip non-functional, so in that case, you'd only get one round fired out of a super-heated firearm. In a auto-loading pistol situation, the grip could act as an insulator, so I guess you would be more likely that the clip could actually feed a fresh round into the now-super-heated chamber, resulting in another bullet shooting out the front of the gun...but.. the gun would jump around from recoil, so it could perhaps stove-pipe... yada, yada, yada...
PE