In 95 my shop burned down. The best estimate is I had 23,000 loaded rounds along with a lot of gun related stuff.
It's mostly true that ammo in a fire will just pop and maybe just throw a little brass a short distance.
BUT from that fire I'm witness to the fact that ammo can also "fire" with enough force to go through steel 50 cal ammo boxes and continue through such things as walls and cans.
There were bullet holes through the shop's paneled and insulated tin walls.
The ammo does strange things.
All the ammo "went off" in one 50 cal can and none escaped the can, while other cans has mutable holes through the can and dents where the base of the case hit the can with a lot of force.
A fist size hole was blown out the bottom of a can that was about 20 foot from the fire.
The can contained 9mm in plastic boxes. About 35 rounds, in one box, apparently decided to "pop" all at once. It's interesting that the ammo closest to the fire didn't blow.
The gun is a Ruger 22 that I had for years.
There were seven guns in the fire but none were loaded.
These are smokeless powder cans, WD40 cans and a couple Black Powder cans.
The WD40 and Black Powder cans blew up.
Note the bullet holes in the couple lower center cans. In order to hit those cans the bullets would have already had to go through a steel 30 or 50 cal ammo can.