ROBIE , The 450/400NE 3" is one of the most versatile chamberings one can chamber a double rifle for! Being a Flanged answer to the 416 rigby, but with lower chamber pressure, it works great in a double! However the 400 H&H is simply the 450/400NE3" for use in a bolt rifle, and is not well suited to double rifle use, being a rimless, belted round!

I have several Mauser actions, and one of them is slated for a .411 barrel, and a chambering reamer for the 400 H&H, as we speak.