no--shoot the hell out if it.
the DOD and the US ARMY fired upwards of 80,000 rounds of steel cased ammo through m16s an concluded the steel case was a non issue.
i have shot plenty of it through the mini and the ar --the only problems i encountered was some of the ammo was poorly loaded. like they used the wrong powder or it was a little weak or very old--
some of the steel jacketed bullets arn't all that accurate some do OK-- in a mini your probably not going to be able to tell one way or the other--LOL--
i have got some very good russian loads of 223 from wolf the 75gr wolf has proved very good shooting and very reliable and accurate from an ar-15.
the only russian ammo i have run across that was real spotty was TULA i got one batch that was way under pressured. most tula is under pressured and slightly under powered, though not enough to fail to cycle.
the mini will probably run some real low pressure rounds the ar series won't.
i recall firing some 40gr loads in a mini and it ran them --in my ar they short stroked-
the steel cased stuff should be fine in the mini--