the DOD did a test back in the 70s and then again in the 80s.
they ran in excess of 80,000 rounds through m16s in the harshest conditions they could come up with.
operationally the steel cases preformed the SAME as brass. now this ammo was loaded to US specs with the same powder and bullets used in m193 ammo.
no extra problems or wear due to the steel cases.
hell even hornady makes steel cased ammo now. it runs perfectly and is fully loaded with ball powder too.
for most of WW2 the US used steel cased ammo.
some US ammunition maker should start pumping out a "budget" ammo with steel case and steel jacketed bullets.
you got steel ammo--shoot it out of the mini.
keep an eye out for buildup in the chamber --try to not mix and match various coated types of ammo when hot . you shouldn't have any problems running it in the mini.
i shoot a lot of steel cased ammo aside from the various crappy powders you sometimes get i haven't noticed that much bad about it. and as much of it as i have shot in the last 20 years surely i would have broke something if it was as bad as people say.