I would say that just shooting to fireform standard brass to a standard chamber is a bit of a waste of time. If it were me, I'd just FL size the new brass (although, all the new Winchester brass I've ever used never really needed it, it doesn't hurt to be sure), load them with your load workup and shoot them. If a particular load seems promising, refine it with the now fireformed brass. Once you've got the load dialed in, load up the remaining cases with that load and use them for practice or even hunting rounds, since accuracy is likely to be quite acceptable.

Why waste barrel life and components when the difference between the FL and neck sized brass isn't likely to be that great.

Mike