Steel cased ammo was employed by the Germans, Russians and Americans during WWII because of shortages in strategic materials like copper (brass). It was never the preferred case material but was a wartime substitute. Armies view military weapons as expendable so steel cased ammo is not a factor for them. It is for me. Steel cases are harder than brass. Steel causes more friction than brass. Friction causes wear. Keep your steel cased ammo. I'll keep shooting brass cased ammo.
Best Regards,
ADP3