Dano4734,
New brass is the same size as is sent to be commercially loaded. If your rifle can't chamber new commercial ammunition, you have a reason to mess with its size. There is another. If you have a case comparator, measure the length of a new case from base to shoulder midpoint. Full length resize it and see if it comes out shorter or longer. If it comes out shorter, then full length sizing the new brass is just increasing excess headspace, making the head stretch further back to find the breech face, and thereby shortening the reloading life of the brass. If it comes out longer, you may actually add a little bit of life to it. IME, usually it gets shorter, however, so I don't usually do it.
The soft, annealed necks can get bent at the case mouth, so straightening the mouths in an expander is not uncommon to do. I don't like to use the expander in an FL sizing die because they can and often do pull necks off-axis. I use a neck turning mandrel in the die body Sinclair makes for adapting them to a press. However, a Lyman M die works well, too, and can add a little step at the mouth to start bullets in straight which reduces runout and improves precision.