Anything can cause an explosion if it generates gases
quickly enough within an enclosed space. Even water,
in a BLEVE with a water heater with overtemperature
and a failed/nonexistant popoff protection.
But it really agravates me to see those 'Hollywood' fires
in which a gallon of gasoline, poured on the floor, 'causes'
an explosion.
Another thing that sets me off is the flashes that are supposed
to indicate gunshot hits.

If I were dead set on blowing stumps with gunpowder, I'd make
some pipe bombs a little smaller than the hole in the tree. With
care about getting powder into the threads.

Crafty wrote in message
...

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