Shooting steel is fine. The problem is shooting brass after. The steel does not expand like brass so you get more debris in the workings of the firearm. This will cause the brass case to get stuck. after I shoot steel cased ammo I make sure to give a quick stroking with a bore brush and some cleaning solution. Use a clean pad to wipe up and go to shooting brass.
I try not to each during one shooting outing. YMMV
Hope this helps a little.