According to bighead :

As I said in an earlier post, true explosives do not need any
confining at all to do their damage.

Precisely.

If you had a flat piece of C4 and scooped
out a depression in it, oddly enough that depression is where the most
damage will be done.

In fact, there's a similar trick you can play with TNT sticks. Let say
you want to punch a hole in a rock. Take three sticks of TNT and
prop them up as a "teepee" above where you want the hole. Fire all
three at once. The shock waves reinforce each other and punch a hole
straight down.

Smokeless powder that is used in modern firearms
is NOT an explosive.

Similarly, black powder as used in antique firearms is NOT
an explosive either.

If it was, the gun would simply explode in your face, REGARDLESS
of whether there was a bullet in front of the charge or not.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.