Have not reloaded any 480's but I do have a box of Hornady factory ammo that will not fit in my FA 475. The rims are too fat for the counter sunk cylinders. (My 475 is a converted gun from Jack Hunnington, not a factory 475). I looked at the specs for the cartridges and the rims for 480 do show to be slightly thicker than 475. According to my Hornady 7th edition manual 475's have a .065 rim while the 480 has .070.

Not sure how this applies but it would seem maybe that a shell holder needs to be 480 specific?

Dan