You will need an action made for the RUM case, a Winchester Model 70 or Rem 700 in 300RUM would be the perfect donor, as would a CZ 500 in 375 H&H. Any H&H length action would work, but the RUM actions already have the feed rails opened up and are easier to convert. The CZ 550 is simply so massive that little internal modification will be needed; that said, you'll need a gunsmith who understands how to make a big bore feed.
Hornady has factory brass and the reports I have heard are that it is excellent; their bullets have received good reviews as well, however Woodleigh softs and solids seem to be the winners in the .404 category.
Hornday either has, or will be producing, factory ammunition.
You can handload any of the 416's to match the 404 in terms of pressure and velocity/recoil, but you can never handload a 416 to match the cool factor of the 404. That huge sloping case gets'em every time
I want one bad to go with my 450/400 Ruger #1 as the Jeffrey was designed to duplicate the 450/400 in a bolt action.
