one important point: reloading dies are steel. Steel on steel produces wear. Brass on steel produces no wear in the steel.
How many rounds will you get before your sizing die is worn to the point of being unservicable? Even with good lubrication, you are shortening the life of your die.
Back when I was young and dumb (as opposed to old and dumb like now
) I reloaded WWII steel .45 ACP cases. Seemed to work ok (except for a small problem with the primer pockets being a little too small
). Only a couple of boxes of ammo, but my sizing die was never the same. Not rrealizing what had happened, I continued to use the die for some time, until I finally figured out why some of my ammo wasn't chambering smoothly. It doesn't take much.
Of course, you may not have any problems at all, but why risk it?