Well, just how far are you talking about? Seems to me you want to know what CARTRIDGE shoots the farthest and not necessarily what BULLET. Is this correct?

You don't need the biggest, flattest shootingcartridge to shoot at targets way out there. It's much more important to have an accurate rifle shooting an accurate bullet and that probably means a custom rifle and handloaded ammunition depending on what you're talking about.

Suppose I had a fully customized .308 Win. (a fairly mild cartridge)benchrest rifle shooting hand tailored match grade ammo and you had an off-the-shelf.300 Rem. Ultra Mag(a much more powerful cartridge) shooting a box of ammo you picked up at Wal-Mart. It would be an absolute certainty (assuming both had the proper scope set-up) that I could hit a 1000 yard target with much greater regularityusing the smallercartridge than you could using the larger, flatter shootingone. Accuracy is not about having the biggest and baddest, it's about having the complete system (rifle, scope, bullet, etc...) that brings all the elements necessary for accuracytogether. Of course, there's no reason why a larger cartridge can't be incorporated into that system, but by itself it doesn't guarantee anything.