It's a pretty good idea to see how big the neck of your chamber is before turning necks - unless you are just turning them only the minimum necessary to get them consistent. Normally, I like to see the chamber's neck about .005 bigger than the neck diameter of a loaded round. Any more and you unduly stress the necks in the resizing process - necks crack early in the process from work hardening, and accuracy is slightly compromised. Any less and you can get into trouble with clearances ona hunting rifle. I have built some bench rest guns where the neck wall thickness was only .008 - and the neck of a loaded round was only .001 smaller than the reamer (6MM PPC); but this is a highly specialized situation with very touchy tolerances.

I do my neck turning on a lathe - using the method prescribed by Mike Bryant. And only on a couple of calibers. The rest shoot good enough for their intended purpose without neck turning. One additional note: some brass is so consistent in the neck thickness that, unless there is a clearance issue that need to be addressed, neck turning is not necessary for most applications. Remington and Winchester brass are not on that list.