Bullet choice will depend upon groove diameter/maker chosen; the 40s range from 0.406"(Shilen) to 0.410"(McMillan) with most others falling in the 0.408" size. 405 WCF is slightly larger, 0.411"/0.412". Many makers will supply moulds in any of these sizes and Barnes offers excellent jacketed bullets in the 0.408" diameter, intended for the various UK 40 cals.

I'm currently in the throes of a high wall 40-70 S.S. build but haven't shot it yet.
Regards, Joe

You can lead a man to logic but you can't make him think. NRA Life since 1976. God bless America!