I have seen the contents of a couple of safes that went through fires.
In these cases, the contents were salvaged with some cleanup, and refinishing of the wood.
One must remember, fire safes do not protect via insulation. They protect the contents of the safe via water production. As the drywall in the safe heats, it produces copious amounts of water vapor. Water vapor displaces Oxygen inside the safe and prevents combustion of contents.
That is why safes are rated for a specific period of time at a specific temperature.
The hotter the fire, the faster the gypsum in the safe is consumed. Another good reason to remove fuel sources from the vicinity of the safe.
Many problems arise when a heavy safe falls into a basement during a fire and becomes inaccessible for days. The contents are thoroughly water logged from the aforementioned water production. Some additional water may enter due to fire fighting efforts. Hell, sometimes the safe is left submerged in the basement.
Usually damage done to guns in a good safe is water damage. That can be minimized by quick retrieval, oil, and elbow grease.
Most damage inside safes that I have seen was caused by smoke (actually "products of combustion" as smoke is mostly ash and the other includes smoke as well as all the other garbage produced in a fire but I'll use smoke as it is easier to write) entering the safe before temps got hot enough to expand and seal the door. This, combined with the water vapor exuded by the gypsum and any that enter prior to the seals activating, combine to produce sulfuric acid along with other compounds that will rust, etch, or otherwise damage that which it contacts. And the smoke residue is a bear to get off. Its been maybe two decades since safe manufacturers began using low temperature activating seals on some safes but even today they are not found on all safes. At least one can purchase low temp seal kits from the manufacturer as replacements.
