Most of the fire resistant safes on the market simply use drywall (sheetrock) as the "fireproofing." Nothing is firePROOF. There are varying degrees of fire resistance. The idea is to keep the guns inside from experiencing a harmful level of heat by the time the fire is over.
Do a bit more research, decide what level of protection you really need. BTW, I've seen a chest freezer filled with meat, AFTER the house burned entirely down, scorched on the outside and only thawed in a few inches. Hundreds of pounds of sub-zero meat kept the center frozen solid. Some people store their important documents in the center of a filled freezer.
Where will the safe be? How long would it be exposed to heat during a fire? How much heat? Is the area sprinklered? Will the area be flooded with water after a firefighting operation? How long before you would be allowed to recover your safe a fire and firefighting operation? All questions related to protecting your guns from damage. Sometimes the ability to seal up and prevent the guns from being flooded is important.