the 375 flanged is a good round that have killed anythink in africa up to elephant in the old times( not that I recommand it for dangerous game, only for leopard). iirc the cartridge was a Holland&Holland development to get the biggest round into a 303 Brit sized double rifle frame. unfortunately today there is no question that the 9,3x74R is the best medium size double rifle cartridge and that is the end for every other round from the 9x57R Mauser upwards. nonetheless the 375 flanged is a good round for anything on feet in north america. I have it in a Wilkinson Mannlicher and the rifle was coming with brass made of Bertram 405 Win.
think the best basic brass today in quality and prize is the hornady 405
http://www.hornady.com/store/405-Win-Unprimed-Cases/