It is completely unnecessary to full-length size new cases for almost all firearms. (You don't think that the ammunition manufacturers do this, do you?). The exception would be a custom-barreled benchrest or match rifle with a very tight chamber.
If your new brass is boxed, so that the cases are separated during shipment, no sizing at all is necessary. If your new brass is bulk-packaged (i.e., loose in the box), it is good to run the necks through the expander ball to round out any dents or eccentricity in the case mouth that may have occurred during shipment. However, there is no need to full-length size.
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The bayonet cannot be abolished for the reason, if for no other, that it is the sole and exclusive embodiment of that willpower which, alone, both in war and everyday life, attains its object.—General M. I. Dragomirov