My current systems operate at 900V, though even higher voltages would be desirable. The most efficient coilgun ever developed was fired at 3,5kV per stage. The second greatest problem encountered in coilgun design is devising a means to switch the power of the discharge, which very frequently runs in the multi-megawatt range. If a mechanical switch is used to deliver the pulse, the very moment the switch surfaces come into contact microscopic irregularities in the switch material will start to conduct the pulse at a higher resistance, dissipating so much energy as to be vaporized right off. When the switch finally closes in its entirety, these vaporized surfaces and the molten metal beneath them weld together, and the switch is thus ruined.
Air gaps are unadvisable as the noise levels encountered are excessive.
The most efficient way to switch the discharge is through a solid state switch. SCRs are currently the cheapest and most powerful solid state switches in the market due to mass production arising from the newly implemented DC power grids around the world. This unfortunately does not mean they are cheap, as an SCR capable of reliably switching a coilgun impulse is not a common market device and tends to cost over 100 dollars. The SCR must have an RMS voltage rating equal to or superior to the maximum capacitor charge voltage, and a peak current rating equal to or larger than the peak current encountered on the circuit during a maximum power shot. The reason for that is because if the projectile was to become magnetized during firing, energy would be lost in the magnetization process which would not contribute to the final kinetic energy.