I'd be concerned with the availability of brass using any of the rimless remington cartridges as a base. The Savage 340 is already set for the 30-30 rimmed case.
In case I wasn't all that clear, the chamber is cut with a 25 Remington reamer (and a separate operation to cut the rim). The dies are 25 Rem but the shellholder is for a 30/30. The cases are formed from regular, rimmed 30/30 brass. The formed cases will look ike a 25 Remington with a 30/30 rim.
