We would have a gun, with a a coil or series of coils as the barrel. The cartridge (say 30-06) would have the projectile replaced with a magnet. If we have the charge & projectile correctly matched to the coil, we could theoretically convert all the energy of the projectile into electrical energy - and use this to possibly charge a capacitor bank for some brief high power use. Such as jumping a car, sending an emergency beacon, firing a laser, etc. I can envision many uses, as well as specific designs for military, aerospace, & consumer use.
As you can imagine, there is some extensive math involved, with many variables to adjust to make the most efficient & safe device.
We could probably start with a 22 cal air rifle for some testing.
At this point it's only an idea, so additions to the team are welcome. I'll leave it here & measure interest as I decide how to proceed.