Re: Need help fireforming brass
If I understand your question properly, these methods will all work.
You can prime the case and put in about 15-20 grains of pistol powder and fill the rest of the case with cornmeal.
Or, you might be able to load the bullet long enough that it jams into the lands and holds the case to the rear of the chamber.
Expand the neck up one caliber and form a false shoulder in your resizing die that is in the right place for proper headspace.