So maybe to try and answer some of your questions directly.
Upper - I think the answer there goes to barrel specs. There is alot of info on this forum, but if your talking long range, then I assume you will want to start the bullet off with as much oomph as practical. That means it probably comes down to either a SPCII or DMR chamber with at least an 11 twist barrel. Some 10 twists seem to work well if they have the SPCII chamber, but I would opt for the 11 twist (or one of Constructor's 12 twist when available). From what has been written here, I would say the barrel length is probably your choice. You gain some velocity with length, but not the same differential typical of larger cases/rounds like classic 30 calibers or magnum rounds. I have an 18" barreled upper that I think is a great all around length.
Ammo - If you do not reload, go with the SSA options in the combat loadings (the oomph part plus the varied bullets they use). If you reload, the sky is the limit. In the hunting section you'll read about great results with Sierra pro-hunters, the Barnes 110 TSX and TTSX and the 110 gr Nosler Accubond (evidenced by Constructor's elk shot). There are really great bullets out there and as a reloader, one finds the right combo for your gun, builds confidence with practice and then executes.
As to the stories, I refer you to the Hunting section.