Re: Converting a CZ 550 to 404 Jeffery,what is needed?
416 Rigby, 404 Jeffery, 458 Lott or 450 Rigby rimless would be those to consider in my opinion. I would stay away from the wildcats and "exotic" cartridges.
22 to 23 inches barrel will do for a 404 Jeffery. Border makes barrels.