eightbore,
When a case is sized, the neck is sized more than necessary and when it is pulled back over the expander, it is expanded to .002"( or there about) less than bullet diameter( to create enough neck tension to hold the bullet). If you size a loaded cartridge, it will be difficult to run the neck( with bullet seated) through the neck portion of the die, and the rear of the bullet will be sized significantly smaller than groove diameter. If you attempt this with a monolithic bullet, you will experience great difficulty.
Mike
