Ammo cans are pretty weak, as far as bursting points go. Some time when I'm bored and I find an ugly one I'll blow it up and film it. I've done it before inadvertently, though.
The latch on an ammo can is pretty strong, and works sort of like a mason jar's latch to seal that rubber gasket and make the can air and watertight. However, the other end of that lid is just held in with six pins made of mild steel - I've bent plenty - that are probably about 3/16 of an inch in diameter if at all.
Open your ammo can, and with it on the ground point the lid up at the sky, then push it to the left. It'll fall off and you can see the pins. They're just held in there by friction.
I blew up one of my ammo cans keeping aerosols in it in the back of a truck. Got hot one summer day and pop! Off went the lid: Bent those pins out. I lost two cans of green gas on that deal, too...
If you lit off a pound or two of smokeless in one I think you'd get a nice pop, off would go your lid, and a big flame out the top. Might light something on fire, but I'd highly doubt there would be any building-rending (or bystander-shrapneling) explosions going on.