When we talk about "locked metal cabinets", what do we mean? Like an office cabinet (light weight) or something more substantial? That would obviously not be fireproof and in a house fire could perhaps put fire fighters at risk. Is fire-proofing not that important?
I use a metal cabinet similar to those used in offices. I could be locked but it is never locked in my house. I am not worried about the "metal cabinet" becoming a "bomb". I am not particularly worried about a burgler taking my ammo either. That is a lot of weight to lug out of the house.