Switching coupled inductors in series while one is charged
As the first approximation the transformer effect can be ignored due the loose magnetic connection between L1 and L2.

Open the switch -> the current from L1 starts to collect voltage to the C. That voltage makes a gradually growing current to L2. It finally sinks the C empty, but there's still a growing current through L1 and L2 if nothing controls the input voltage. In practice it soon develops to a short circuit. This happens already when the switch is on, if the input voltage is a constant DC without another control somewhere.

If your input voltage comes from a charged capacitor, this circuit is NOT impossible. L2 really can have it's max current at the right moment and the resonance can return a substantial part of the energy.

This circuit is quite easy to simulate if you know the inductances. You can assume max. few % coupling between L1 and L2 and see its effect. The effect of the projectile needs experiments or some ultra high cost software that needs a phd to input all parameters properly.