Hi Altamaha. If the .400 is based on the .375H&H case and due to its long neck has less powder capacity than the .416 Rem Mag. The COL of .400 is 3.55" compared to 3.6" for .416. The .416 also has a slight advantage in volumetric efficiency(.416 vs .411).Can you explain how the H&H can produce 2400fps at lower pressures?
Since we already have the .404 NE,the.416 Ruger,Rigby,Rem, Dakota,Wby and I'm sure I forgot a few like the Lazzeroni Meteor and I won't mention the wildcats, I fail to see any advantage to the .400H&H other than the status associated with the Marque.
It requires a magnum length action,and for most will be a handloading proposition due to cost and availability of ammo. The .416 Ruger will push a 400gr at 2400fps from a Mauser 98. The Ideal for me to build a proper rifle would be a .416 based on a shortened (2.5") .404 Jeffrey case. Maybe Nosler will produce it in a few years. Greater powder capacity than H&H with shorter stroke of Mauser 98.