I stuck a .300 WM case shortly after I started reloading, I scrounged around the garage and managed to find a tap, screw to fit it, some washers and a socket. Basically the same thing as a stuck case remover but with makeshift components.
The process is straight forward, drill out the primer pocket then tap it, put the cup(in my case the socket) over the die and thread the screw through the washer and cup into the case. Then it is as simple as tightening the screw until the case pops free. The case is obviously ruined but the die will be perfectly fine.
Just remember to back the decapper out of the way so that the drill or screw doesn’t hit it and break the tip off.