That’s right. Most gunsafe manufacturers use sheetrock for fire protection. It’s cheap, and highly effective. A typical gunsafe may have over 100 lbs of sheetrock inside of it. Moisture, normally trapped in the gypsum mixture, when heated above 212 F, turns to steam and escapes. Turning all that moisture to steam requires the heat energy that the fire may be putting into the steel safe body, and will hold the internal temperature of the safe at approximately 220 F until the sheet rock has dried out completely.