I may have posted this on the last thread on the subject, but I took time to chat with one of the captains at the nearest fire station when we moved here. I asked how he felt about loaded ammo and bulk powder. The answer was as long as the bulk powder is in the original container (except for those really old metal cans with snap on or screw on lids) they had no heartburn about it. Apparently the newer plastic/paper cans are designed to melt or burn away before the powder ignites in the confined space of the can. It just spills out and burns up. He was even less concerned about loaded ammo. They have worked houses with loaded ammo before and their turnouts deflected the few cases that skittered across the room. Maybe he was just being a tough guy, but he pretty much waved me off.
I've seen the aftermath of military ammo dump fires and the loaded ammo cans not cracked open by the original blast - RPG, mortar round, whatever - look exactly as described above. Paint burned off, a little bit round on the sides with dimples here and there, the lid still firmly locked and no penetration holes from the inside.
All that said, I really like Jmann's idea of a separate blockhouse. Kind of hard to do here in the homeowner association controlled yuppie 'burbs, but I'm headed for the countryside shortly and have the perfect hillside to bore into.
Finally, way to go Hotchkiss. Now I have to deal with fire truck envy. . .