I like the 450/400 3 1/4" Nitro Express Magnum.
The 450/400 3" Jeffery is the same ballistically, and its thicker rim is probably better..... But I just like "That impossibly long skinny neck".

Either of the 450/400's are the best all-round double rifle cartridges on the Planet.

You will NEVER go wrong with a 450/400.