I'm current researching doing something close to this. I plan to expand the neck out to take a .411 bullet. I have a Siamese Mauser that has been collecting dust and I have just picked up a .411 barrel with a 1-18" twist. Everything I have found indicates that I will be able to use a bullet that measures less than 1.4 inches and weigh less than 430 grs. I'm planning on 325 gr - 350 gr cast bullets.
I believe I will have something very close to the 405 Winchester or maybe a .411 Hawk.
The brass should be strong enough since the base cartridge runs pressures somewhere between 308 Win and 30--06 Springfield.
I'm sure I could go with another case, such as the 30-40 Krag or the 303 British but the one common thread between all these cartridges is that nothing of them will require gunsmithing to the bolt face or feed rails.
CA Dude