7stw is right, some of us have a press designed to cam fully over with all dies, some do not and have to be more careful. The RCBS Summit I now use is a cam over press. That along with the shell holder movement and side/fore and aft movement changed my world and got me loading straighter more concentric cartridges.
I know there are some that don't believe concentric ammo is necessary or any more accurate..........I find I'm never swayed by debate when compared to real actual hands on results and experience with something. When I talk about collet/mandrel neck dies, press movement to help align cartridge to die, camming over with dies, removing spindles and expander ball's and rotating the cartridge several times when seating its because they have all worked together for me..........if it just plain works I make it a part of my reloading process.
At the same time I have changed from neck sizing only and incorporated a full length sizing step, also really changing the way I flash hole deburr if at all as well. I never intend any offence just one persons way of doing it. It's what makes this site great!