According to Crafty :

Firearm misfires will readily breech carbon steel and blow your face off.
It happens. Gunpowder is explosive under pressure.

Smokeless powder will do the same thing under the right conditions.

Heck, we can get a chunk of wood or ordinary plastic to "explode" by
that definition.

Does that make wood or plastic pipe an explosive?

I suspect not.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.