Military steel cased ammo can have harder primers and some civilian rifles have trouble setting them off. Some rifles can shoot it without problems but others need multiple strikes to set off some primers.
I once got almost a full box of "dud" 308 Barnaul rounds from a guy with a Browning because his rifle couldn't set them off even after multiple strikes. I had a Norc M305 at the time that fired them without issue.
There is no universal rule and it is a trial-and-error process depending on the specific rifle and different brands of ammo.
I have read online about horror stories in semi-autos with steel cases rupturing and splitting stocks/blowing out mags. Those are mostly M1 Garands and M14/M1A's though; not civilian rifles.
A friend of mine had a problem with the copper from copper washed Norinco FMJ 308 leaving copper in his chamber. Some copper solvent cleared it up easily.
I've never had issues with steel cased ammo in any of my civilian rifles.