The metal piercing rounds in both .38 Special and .357 Magnum were designed to shoot into cars when they were actually made out of real steel, and had more than a modicum of metal in the doors, etc. The mobsters of the era outgunned the police, who were mostly armed with .38 Special round nose lead bullets, which wouldn't penetrate through car doors. These were designed to alleviate that problem. The one I pulled had a truncated metal nose, and a lead bearing surface, but I don't remember which brand it was, as it was many years ago.
They weren't designed as armor piercing rounds, just metal piercing, as in car doors.
Hope this helps.
Fred