I noticed there is ammo called Black Bear. It is steel cased. The first two links show where I found it. I never heard of it until now. Apparently, the bullet is lead with a brass jacket instead of steel.
https://www.cheaperthandirt.com/pro...862994.do?sortby=priceAscend&refType=&from=fn
http://www.luckygunner.com/223-rem-55-grain-brass-fmj-bt-black-bear-500-rounds#info
https://www.cheaperthandirt.com/pro...862994.do?sortby=priceAscend&refType=&from=fn
http://www.luckygunner.com/223-rem-55-grain-brass-fmj-bt-black-bear-500-rounds#info