You also haven't touched upon nanites. They would be too small under the field conditions for most people to see, or hear coming. They wouldn't need more explosive than they could carry if they fly into a human ear canal, open mouth, or up a nostril before they explode.
Think fire ants swarming on the ground in legs with an tiny explosive stinger. They could also take a small amount of steel away from a machine by stinging it. Bit by bit wear the machine down with tiny explosions until it's all gone. A 155 melts away before their very eyes