Be sure you neck anneal those cases after you expeanded the necks!
I've necked up/down several thousands of cases in many calibers, and almost invariably with caliber change, the necks will crack on loaded ammunition because the work hardening and loaded bullet strains them.
It's easy to do. Stand the cases in a pan of water, exposing the last inch of the neck/shoulder. Using a propane torch, pass the flame on each case until it starts to discolour (turns straw, then blue), and tip the case into the water to quench. Naturally, you don't tip over primed cases.
HTH
John