VC, the 375 NE 2 1/2 is a rimmed cartridge and is not what you are after.

The English designation for the 9.5x57MS is 375 NE 2 1/4 Rimmless.

The 2 1/2 is straight taper case which is why the die set is three piece as it has a mouth flaring/expanding die included.

Regards, Matt.