good discussion Carguychris.
Ammo should not be stored in uninsulated unvented metal cabinets. Radiant heat will rapidly increase the temperature inside the cabinets to the auto ignition temperature of the powder/primer. When that occurs the ammo ignites. If the cabinet in not vented the burning propellants will generate pressure, accelerate the burn until until it reaches detonation velocity. Once detonation velocity is achieved the cabinet turns in to an excellent IED.
I store my ammo in wooden foot lockers. These lockers are locked and located in numerous locations throughout my property. I maintain a basic load with each weapon. 5 mags with my 1911 nest to my bed. 4 30 rd mags and one 10 rd mag with my ar.
Storage boxes are located were I may need them at strategic locations on the property.
By separating the storage I minimize the fire risk and improve my defense plan.