I work with fire safety regs. in my daytime job.
To help protect your guns against fire, buy some 5/8 inch sheetrock, and a 1 gallon bucket of drywall joint compound. 2 layers of this sheetrock (drywall) will withstand 1 hr of fire in an open enviroment, and possibly longer in your safe. Cut the sheetrock to fit tightly at all joints, and use joint compound on those joints. Don't forget to do all 6 sides.