I believe this is generally true but I also wonder if there was a specific (popular) hard-cast that caused early trouble and led to this whole rule. I never had an issue with BB's hard cast 220's in mine but then again my G20 is also a former police service duty pistol and while not "shot out" yet at all, the bore's definitely not new. Maybe that helps - I'm no armorer. You might also mention BB's "dangerous game mono metal" option if he wants another option? I haven't tried them myself but I've heard good things...