I have shot steel case ammo in the past with the only issue being the occasional failure to eject. As for damaging a gun I would think that would be rare but I have heard that steel cases tend to wear on the extractor / ejector parts of some guns. Which makes some sense with these being the parts that contact and move the cases the most.

they are dirty which can cause extra wear

Phillip. no Sir. Steel does not expand like brass so will not seal as well and will produce more blow by or residue in the chamber (dirtier it up quicker) and require more frequent cleaning intervals.The firearm uses heat treated steel and steel ammunition cases are mild steel so no other worries. Cheers!

Phillip, No, steel case ammo does not damage firearms. Sure steel cased ammo has its idiosyncrasies, but will not inherently damage your gun. If it damaged guns they would not sell much of it.

The problem with steel casings is they do not allow for expansion as brass do this by itself not a problem but the problem can be with extraction/ steel can leave markings or scratches on ejection port and further wear to ejection areas but overall not a major problem they are also not reloadable but easier to pickup ( magnet) so in overview if you are just practicing and you do not shoot often the wear would be minimal but to an avid shooter wear could be substantial especially with rapid fire and excessive shooting/ wear for an avid shooter could start as early as 3 to 5000 rds and possibly shoot out barrel by 10,000. The only other issue in my opinion would be moisture as steel would rust and attract moisture so if ammo is to be stored for any length of time I suggest brass