A shell holder can be modified quite easily. All it takes is a solid flat surface, a piece of glass, I use the cast iron top on my table saw, some form of light lubricant (WD40) and some 800 grit "wet" sandpaper. Take a measurement before starting to modify the shell holder, place a fairly good amount of lubricant on the wet sandpaper, hold the shell holder down flat on the sandpaper, with heavy downward pressure drag the shell holder across the sandpaper in as long of a stroke as possible. Keep up this process until you have removed as much metal as needed for your particular application.
