The bottom line is that neck dies and bump dies have been replaced by closely fitted (moving minimal brass) FL dies. Harrell dies are made with small incremental differences on CNC equipment for the PPC and BR calibers.
When you send Lynwood a tight fired case, he will use it to select the proper sizing die for your PPC from a dozen or more versions that he has sitting on the shelf. These dies are a bargain, and are very commonly seen at matches, because they work so well. Bump dies do not address one of the two areas where cases get tight, just above the solid head of the case, and for that reason are not of much use to shooters who shoot PPCs at what have become normal pressures. If you are going to work with a small set of cases, you are better off using a FL die, that fits, every firing, and closely monitoring shoulder bump (as compared with a tight case).