I have reloaded 30-06 and .270, and just picked up a 300 win mag. I am confused about the case seating, and how that relates to reloading. Do factory rounds seat on the belt, and then once sized, they seat on the neck? Does this mean you would have to sight in for each scenario. Is factory unfired brass going to seat differently than sized brass? Anyway, if someone could provide a short, 300 win mag reloading for dummies summary for me, I would greatly appreciate it.