1) Some stout metal pipe
2) heavy duty plug (fits firmly in end of pipe)
3) Some fireworks, or any other source of black powder
4) Some sodium (pure) or potassium
5) Wadding
6) Match or other ignition source

Mould 4) into small balls, ~2-4mm diameter.
Plug 1 end of pipe with 2).
drill small hole in plug
fill pipe with contents of 3) making sure some fills the hole.
top up with balls of 4)
add 5) to keep everything in place

aim at boss
apply 6) to hole in 2)

Of course, you may want to do the last step by remote

MuahahahaHAHAHAHAHAHAHAAAAA!