That's cool, too. Propellants have always intrigued me more than the explosives, though.
You really should build a trebuchet, at some point, though. You would probably love it.
We made several as kids, but my brother and I once made a fairly large one out of some scrap Aluminum extrusions we found at a salvage yard. The extrusions were used to strengthen a pair of twelve foot 2x4s and build the frame/base. We were in our twenties, then, and had some understanding of the forces involved, when we built that one. It worked very well. Not sure why, but the memories of that device hit me last night. Now, I want to build one, again, but I have too many half-finished projects going, already.