Scott - and others, I hadn't considered loading the .405 up to the ballistics mentioned, only going on factory 300gr. ammo. I-too felt the factory bullets too soft for buff,(no experience on them) but know for a fact, they work well on N.American big game to and have worked on big bear when necessary.
: A 400gr. at 2,000fps or greater or heavily jacketed 300 at 2,400fps would certainly do the job. The bullet and placement being the main criteria.
: Properly placed, even the 300gr. factory ammo would suffice, if one has the discipline to not shoot until a perfect shot is presented. Just where that would be on a buff, I don't know - but I am sure there are fellows here who are capable.