The .470 Capstick is the .375H&H necked up and blown out, but it is not lengthened.

You can start with .375H&H, .375 Basic, .416 Remington, Hornady's Basic belted magnum, or .458 Lott brass.

When I start with .375H&H brass, I take it up in steps: .375"-.400", .400"-.450", .450"-.475". The result is a wasp-waisted case; a 70% charge with 400gr. bullets blows it out to final dimension.

George