I have .400 Cor-Bon barrels for my G21, G30, and 70 Series Gold Cup. I've fired thousands of rounds through the G21; a few hundred through the G30 and a few hundred through the G.C.
I've also responded to several threads on this forum about reloading .400 Cor-Bon, etc. I believe that you'll find a few threads about .400 Cor-Bon if you'll do a search.