my first guess would be wood over plastic, in that if your safe is air tight, the damage would be by excessive heat. The wood would turn to charcoal with out air, the plastic would turn to a drippy mess over everything. I guess if would all depend on how air tight and anti-o2 measures would be in effect on your particular safe. However, in that case, i would suppose the same would have happened to the synthetic stocks as to the plastic and the wooden stocks with he wood so maybe your guns would be ruined in either case anyway if it got that hot, so in that regard it wouldn't matter then. But I doubt it would matter much if you have a decent anti-fire (heat) safe anyway. Best would be to keep hot burning substances far from the safe, encase the safe with asbestos and then with fire brick to blockade it in from all that heat in the chance your home burns down.