Part of what you typically get with cheap gun safes / Chinese made gun safes is insulation made up from construction scraps. The pictures below show a new Chinese made safe in our shop for service. Notice that the drywall is pieced together from different kinds of drywall. The light and dark pieces are even different thicknesses. They are glued into place and the seams are mostly covered with tar-like glue. Some of the gaps are quite wide, which naturally allows heat to pass in a fire.
In the light colored pieces at the lower left, you can see hammer marks from when these pieces were broken out from whatever they were previously nailed to. Look close and you can see boot prints. In a number of places the paper backing is loose – it pulls away from the gypsum when the pieces are broken apart carelessly. Frequently with this type of junk safe, the drywall pieces will be smaller than what is in this safe, as small as 5” X 5”.
Remember a few years ago that many homes, especially in the southeast U.S., were left uninhabitable by Chinese drywall with very high levels of formaldehyde? Well, that same drywall was (still is ?) used in Chinese gun safes. I have read that those formaldehyde emissions promote rust (guns), as well as lung cancer, heart disease, etc. Do you suppose they still use that crap in gun safes? What do you think happened with all that high-formaldehyde drywall? Where in the world could you possibly re-use that stuff? Think about it.
Do yourself a favor: Buy an American made gun safe.