Please be advised that we do not recommend the use of imported ammunition, as it may be corrosive to your rifle. The foreign surplus ammunition may also cause the gun to misfire or mis-feed and in extreme cases can cause the firing pin to break.
This would concern me more than the steel cases tearing up the bore. This is the first I've seen that Ruger actually states the ammo may be the cause of broken firing pins. The problem with the broken firing pins is the rifle needs to go back to Ruger to have a new pin fit to the bolt. I imagine you'd have to shoot a lot of steel cased ammo to destroy the bore of a Mini-30. Anyway I hope the rifle's all better now.