No explosives in this story, but I think it's in the same spirit.

One of my college friends made a blowgun out of a 6-foot piece of electrical conduit. (Ours was metal. Nowadays they also make it out of PVC plastic, which I imagine would work just as well if not better.) We made darts out of nails, fitted with a cone-shaped paper "tail" to fit snugly in the tube. You want it tight enough to get a good head of air pressure behind it, but not so tight that it causes a lot of friction as the dart slides through the tube. Very low-tech, but potentially lethal! With practice, we got so we could fire a dart into a two-by-four so tight you needed pliers to pull it out.

Say, I wonder if you could get one of those through airport security?