It depends on what you mean by "clear step up". If you mean that the upper end of the useful range of capability is noticeably above that of the Creedmoor, then somewhere around 7 mm Mags shooting 150 gr bullets faster than 3000 fps. If you mean no overlap between the top of the useful range of the Creedmoor and the bottom of the range of the other, then I would guess somewhere around a 338 Win Mag.
