The 500 Cyrus was developed by wildcatter Michael Cyrus of Cross Outdoors, Prichard, WV. The idea was to provide a big-bore rifle with a shortened action of less than 3 inches that would be capapble of giving 470 Nitro type stopping power, as well as to take advantage of the new wave of .500-caliber handgun bullets. It is based on a shortened 416 Rigby case with a rebated rim.