If the nano bow is meant to shoot energy why not just change it to rifle or maybe a handgun? To me a bow seems out of place from the rest of IC's weapons.
If your trying to make it different from the mining laser then I'll offer my explanation for how the mining laser works: I believe that the mining laser is actually firing plasma instead of light, the plasma is being contained by a magnetic field that is generated by the redstone as the plasma is fired. By adjusting the intensity of the plasma and magnetic field the behavior of the bolt can be changed allowing all the interesting modes the mining laser has.
Either way just my two cents, and I'm loving this mod and would definitely call it my favorite IC2 addon.