What I was wondering about last night - a) fuel air pretty much relies on overpressure, throwing the casualty into objects, or (less so) firing objects at the casualty. In bare-arse terrain you would think that fuel/air would work less well. Suppose the packet was surrounded by shot/foil blades/something similar. The packet pops and sprays the fuel and foil and then the spark initiates the bang. Would some of the foil blade (I'm thinking something the dimensions of razor wire) hang in the air long enough to be driven by the blast? Things fall 10m per sec ignoring air resistance, but air resistance can be significant with some things. Would falling through a cloud of fuel slow it down further? If it fell to the ground might it get usefully driven by the blast anyway? If it was light enough to work would it be too light to retain velocity? It just seems to me that a fuel/air bang in open country looks impressive, but in the absence of fragments might not achive much. b) How fast does the cylinder of a car engine move? Could you fire a mortar round with a tube and a bomb with a base plate acting as the "piston" in the cylinder, and a combustion chamber at the bottom, fuelled by a little bottle of petrol? I'm guessing that you wouldn't get enough velocity, and the weight of propellent saved would be low.