John,

The 378 case is essentially a 416 Rigby Improved and with belt added and 30/378, 338/378, 416 Wby and 460 are the 378 case necked up or down. The are a few grains larger than the 416 Rigby case.

300 Wby and 340 Wby are basically the 375 H&H Improved neck down and the 375 Wby is a 375 Improved

257, 270 and 7mm Wby are shortened 300 Wbys necked down. They are similar to 7mm Rem case but with longer necks.

240 Wby has rim and belt diamter of 30/06 head size and thus is slightly smaller in body diamter than the 30/06. But with the thinner Norma brass and less body taper the case capacity is about the same as a 6mm/06

The extinct 224 Wby is basically the 219 Zipper Improved or 225 Winchester but with a belted case.

And all the Wbys have the double radius shoulder which gives them the look that the chamber was cut with a worn out reamer

Mike