30 cal. = 168 TTSX or possible the 150 TTSX depending on distance.
As BuffaloBob stated, it would get awfully boring wouldn't it?! What would we do with all of our time spent trying different bullet, powder, brass & primer combinations? Dear lord, I think i'm about to have an anxiety attack.....
Well, guess that would be a .30 caliber 150 gr. Hornady SP or Sierra Pro Hunter SP or a Remington SPCL Core-Loct; all three have done me very well. The biggest white tail I ever saw wouldn't be hard to kill so no costly premium bullets are needed.
If I could only have one rifle and one bullet it would be my Rem Sportsman 78 action Shilen select match SS #6 26" 25-06 in an H&S Precision stock with Zeiss 3-12X56 and the bullet would be a 117 Sierra Pro Hunter.