25-20 SS cases can be made by pressing 223 up into the neck of a 7mm die with an arbor press and a punch then turning the case ahead of the rim. There is a bit more to it, but I've only seen it done once and that is the part I remember. It's not an easy job, but that's about the only way to come up with a good supply of cases unless you are independently wealthy and like spending your money that way.