Well Nuke, I can tell you that its not happening much.
During a military exercise, I attended, some lamer had to go smoking in the small arms munition storage. and you know the law of Murphy. It catched a fire, of course.
Now, what to do? Open the door, throw in the foamhose and fill the place with foam, while the rounds was poping of.
The inspection showed that no bullet had penetrated the ammocrates while exploding.