I'm always talking about how 'pretty' the .350 magnum cartridge is, but the 400/350 if anything is even prettier. I believe John Taylor, who loved the magnum, also said he preferred the 400/350 because of its heavier bullet. If I'm not mistaken, the 400/350 was the first cartridge offered by Rigby for the magnum action, around 1899-1900. Original Rigbys in 400/350 seem to me to be much rarer than the .350 magnum but are priced about the same.