I have a rebored/re-chambered .303 into .35 Winchester. Very handy cartridge shooting 200-250 grain projectiles. Ballistics are very similar to 35 Whelen but about 200 fps slower. Brass is formed from the 30-40 Craig. So, for the price of a Merkel 470 I got a real Holland and Holland double rifle, and; I can go shoot my Ruger H-1 .458 to remind me why I don't like recoil.

I still thing the 450-400 would be great. Mild recoil, factory ammo and easy to reload.