Thanks for the replies. I created a simple cutting mechanism by taking a piece of 3/8" iron gas pipe and screwing it down to my work bench, measured out so that a razor knife could cut to the right length. Then I took the bolt out of my razor knife and put a screw through that hole and into the side of the bench. The knife pivots on the screw, contacting the shell, which is placed over the pipe, and cutting it as I hand turn the shell. Turned out pretty handy and cuts very straight and cleanly. Cost me about $4 for the section of pipe and some new razor blades.
Now, I will just have to see if I can get the shells to roll crimp.