A high-current inductor, and a sudden thought — could it make a coilgun; clamp it in a vise to test; push in the projectile; the resistance is tiny so it needs a high-current source, which brought the spot welder to mind — mine peaks at 650A with an output of only 4.2V, and if it works this is an ultra-low-voltage coilgun; try it straight away, decent power, you can see the recoil; the improved version has a thicker coil and only needs a press, no sparks, push in the projectile and try, efficiency seems a bit lower because the gap is a bit big; back to the original — truly the most powerful coilgun with the least copper; see you next episode. Comments: go study engineering, hand-build god (3); only 3.7V? the instantaneous high current makes the field that pushes it (creator: spot welders are all 1S or 2S, mine is 1S); a 310V one only manages this much; bubble-tea straw as the rail, thin is the point; could a supercapacitor be the power source.