A customizable case former and it system and method of use provide for a case former having a base, interchangeable case gages and forming heads. Contained within the interior of the base are slide blocks mounted on slide rails and assemblies in such a manner as to allow the slide blocks to be slidingly reconfigured to form a case forming cavity of varicose sizes and shapes. The size and shape of the case forming cavity is established and maintained by a template opening, defined by, and potentially unique to, each case gage. The size and shape of the forming head corresponds to the size and shape of the template opening. The slide blocks are secured to the case gage by removable locking pins.