When I first started out, I got both the fired and new brass case holders for .308 Winchester. Never used the 'new' case holder, only the 'fired', so when purchasing case holders for other calibers, I never bothered with the 'new' holders. There isn't exactly a high demand for them so I was pretty much stuck with it acting as a paperweight, etc.
Last year, I finally found a (real) use for that 'new brass' .308 Win case holder: virgin Winchester .308 brass. That stuff is so grossly undersized in about every dimension right out of the bag that its just ridiculous... and it slides too far into a 'fired' case holder. But it fits in the 'new' holder like it was made for it...
Generally speaking, I'd say you're just about as well off to take the virgin brass, expand/round out the necks, chamfer the inside, then fire them for load work-up, practice, whatever. *Then* worry about trimming. I don't think I've ever had virgin brass, of any make/caliber, that was too long. Yeah, there may be some slight variation in OAL... but until that shoulder gets blown out to fit the chamber, there isn't a lot of point (in my mind) in worrying about a precise trim length.
YMMV,
Monte