yes its been done before. even tried to make 30 luger out of them. too much work in my opinion, case mouth has to be thinned for bullets to seat properly. rims diameter vary as well on 223 so its important to have same brand of case .
i'm lucky to attend a range where 7.62 tok ammo of all sorts being fired so S&B, PPU and Fiocchi cases can be found in scrap buckets. after a while i dropped the conversion efforts and just reload in proper brass.
Starline cases are pretty affordable so no point in wasting that time