Re: what caliber
Nothing wrong with the 270 for 500 yard whitetails but if you feel like toying with another caliber on the 270 bolt face then there is a whole host of great options. The 280AI running 162 AMAX's, 30-06 running 208 AMAX's, 284 Win running 162's, 308 (178 or 208) , 708 (162), 260 (140), 6.5x284 (140) are all great 500 yard whitetail calibers.
For a long action standard bolt face 500 yard whitetail rifle, the 280AI and 30-06 would be my top 2 picks in that order.
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.