Here are the problems with steel cased ammo and the AR.
1. The steel cases don't expand to create a good seal, letting the gas to escape into the chamber (Steel cased ammo is much ddirtier also) Each time a cartridge is fired you get more residue build up in the chamber. Each chambered case packs the residue tighter until you get s stuck case from getting wedged in the residue. Combloc calibers have the same problem but because the case has tapered walls its easier for the extractor to pull the case out. AKs and SKSs you don't even notice it.
2. Steel cases are bad for cheap extractors. As the extractor heats up, the steel case wears the extractor out.
3. Bi-metal bullets that always accompany steel cases are just bad for barrels, Any barrel. Better made barrels wear better but will still have a shorter life that barrels shooting only copper jacketed rounds
1. The steel cases don't expand to create a good seal, letting the gas to escape into the chamber (Steel cased ammo is much ddirtier also) Each time a cartridge is fired you get more residue build up in the chamber. Each chambered case packs the residue tighter until you get s stuck case from getting wedged in the residue. Combloc calibers have the same problem but because the case has tapered walls its easier for the extractor to pull the case out. AKs and SKSs you don't even notice it.
2. Steel cases are bad for cheap extractors. As the extractor heats up, the steel case wears the extractor out.
3. Bi-metal bullets that always accompany steel cases are just bad for barrels, Any barrel. Better made barrels wear better but will still have a shorter life that barrels shooting only copper jacketed rounds