The amount of case prep work you do depends on how uniform you want your cases. At a minimum, you need to de-burr and chamfer the case mouths. If you see copper shavings on your shell holder, you are not chamfering enough. If you crimp your cases, then you have to trim the cases to the same length, otherwise, you will have different neck tensions. If you want ultimate accuracy, go to precision shooting, bench-rest shooting and long-range shooting websites. They will take you places you probably won't want to go. Like, I have a tool that chamfers the inside of the flash hole. It's a rod you insert in the case mouth, with a guide that fits in the flash hole, and a chamfer section to clean up the inside of the hole. Don't laugh, the best part is there is a collar that fits over the rod with steps to fit the various case diameters, so that the rod is centered on the case.