[Riley]

My guess is that a cartridge in a fire would behave like a mini hand grenade, with a range of a few feet or so.

I wouldn't even go that far.

One of a hand grenades defining characteristics is lethal fragmentation. Uncontained ammo burning is more like a firecracker. Lots of noise, lightweight bits of brass casing fly around. If your eyes are protected you're probably fine.

[KC Burke]

Semi-Auto ammunition is a problem, it is semi explosive like an automobile. If it is “assault” ammunition that is where the real danger resides.
< /Sarcasm >