Rick
It is not the BC it is the cordite burn rate pressure curve that is the issue. Also the open base changes things in cordite used barrels that flat based cant copy. Depending on how used the barrel is boat tails may not work at all. Forget trying to make it a vermin shooter or use 3031 to emulate cordite. .312 projectiles will be your friendly ones. I convert 174g OBBT to straight 174g BT to solve the cordite barrel issue but can not get a perfect match to Mk7 on the drop sheet. As said else where have fun.