RE: do i have to resize brand new brass
Up until I recently I've always procured rifle brass by firing factory Winchester ammo. This, of course, fireforms the brass to the chamber in question, and from there I just neck size it.
But recently I did buy a lot of new unprimed Remington 7mm STW brass, and found that they did need to be sized for no other reason than the necks were anything but round (apparently new brass isn't handled with any type of care as some of the necks were really dinged up). I ran them through a FL sizer and found that the die barily touched the case other than the neck, so in this case FL sizing wasn't necessary. The primary purpose was to get the necks back into round so I could trim, camfer and deburr them.
Mike