I have fireformed and necked down more cases than I can remember for wildcats and have used the same method for decades. I won't go into necking down, since it is much more complex. To expand anything, I set the cases in a flat pan of water to a point above the head of the case, take a propane torch and go up and down the rows, heating the exposed case until it is red, then tipping the case over into the water. Then I prime the case, use 3 or 4 gr of Bullseye, fill the case with cream of wheat and stick the neck into a bar of ivory soap and snap the plug off. Ivory is cheap and pure(remember?). Fire it off and you have a case, which is probably hard again at that point.
One thing I found when trying to make Paradox cases for an odd German Cape gun I had. Brass is very unforgiving. I started with 20 ga brass shells cut to length. annealed the mouth and loaded round ball rounds with a Paradox style crimp over the ball. Not excessive but just enough to hold it in place. The crimp was easy in the freshly annealed case. After one firing, I could not crimp the case without a new annealing. I gave up on that and simply glued the ball inside the case like an overpowder wadin a brass shotshell.
