Good question. I haven't reloaded in several years (but am resuming this yr.). I would think it would be hard on the dies, maybe not the carbon dies. Might be worth looking into. What kind of steel casings do you have?
Trying to resize steel in a steel die will wear your dies out quickly. The varnish will also wear off, causing them to rust and lose structural integrity. Also, a lot of steel cases are berdan primed so it would be useless to even try. As cheap as surplus ammo and once-fired boxer-primed brass is for the various 5.56 and 7.62 chamberings, I wouldn't bother.