If you're going straightwall with a shortened H&H case, you can make a .475"
Wouldn't be any problems with the ammo being run into a full length mag chamber.
You would need to inside ream the brass to seat a 475 bullet...also the choice of 475 bullets in lightweight pointed are non existent...my idea is for a cartridge that is accurate yet able to take a 200 yard shot across a bean or corn field with minimum drop.
450 Marlin brass has a larger belt on it so it will not chamber in a 7mm-300-338-458 ect. gun....I think a 458 WM if cut to 2.1" would chamber.
If somebody is so dumb that looking at a short fat cartridge thinking a big fat bullet is going to go down a 264-7mm-300-338 hole in the barrel they should be removed from the gene pool.
