Clark,

We all eagerly await you .577!!

In regards to the 450/400; at one time it was the {only} cartridge I was considering in a British double - that was - until I stumbled on the buy of the century and picked up a 500/450 and fell in love with that cartridge. I was able to closely match the ballistics (recoil) of a .375 H&H, 450/400, and a 470. Colorado owns the rifle now and has become a big fan of the 500/450 also. I think the cartridge is little known because there a so few rifles chambered in it and it is over shadowed by the 500/465.