Re: fire forming without a bullet
I do the same COW process only with Corn Meal. Gives the process a bit of a Mexican flavor.
Be careful of a ring being built up in front of the case mouth.
Fire forming with bullets also works well, to go along with the above two comments, but I always do the COW thing first, then finish fire forming with a bullet which is fired during a hunting event. There is a difference in performance between the final fire formed case (the shot after the COW process) but not enough difference to worry about except at distances over 850 or so yards. Note this is in an extremely over bore extreme magnum cartridge. Well beyond most if not all AI cartridges with a short barrel life expectancy.
I may be the slowest guy on the mountain . . . . but . . . . I'm on the mountain!