What Happens When Ammo Burns? Sporting Ammunition and the Fire Fighter | SAAMI.org

Most bullet cases are made out of brass. I'm no rocket scientist, but brass cases would make a horrible rocket engine material. The only reason cases don't catastrophically fail when you fire a gun is because of the bolt/chamber providing support. Brass IS pretty good about stretching quite a bit before a catastrophic failure. This property is what allows case fire-forming ( [LINK] ). It's also a pretty awesome safety feature. Cases are so bad by themselves about containing the force of expanding gas, that ammunition fires aren't nearly as dangerous as you might expect them to be. ( [VIDEO] ) It's a long video, but if I recall correctly, it demonstrates that a rifle cartridge fired without a chamber doesn't have the energy to penetrate cardboard at like an 11 inch range.

Ammo cooking off in a fire sounds dramatic but isn't particularly dangerous [0], unless of course a loaded gun is burning. In the OP's position it would be really low on my list of priorities. [0]: [VIDEO] (skip to about 13 min)

Even if it does go off, as long as the rounds are not chambered it's really not that big of a deal. [VIDEO]

Again, wrong. Ammo is not dangerous in a fire: [VIDEO] As for humidity, I think you would be surprised. Much of Appalachia and the East Coast have high humidity levels (typically 70-90% during summer IIRC) and I've never found ammo damaged by humidity there. I've shot 25 year old ammo that was put in an ammo can and dumped in a hiding spot near a pond (so, very high humidity) and had no issues shooting with it. Even if the ammo is stored in the manufacturer's cardboard box, I wouldn't worry about humidity damage unless average levels are over 85 or 90%. Water damage is a different matter, but I don't have any experience with that.