You need to shoot a little bit more to get proficient at longer ranges. 6.5creed and 6.8spc are not great elk cartridges. I think you are on the right track with just shooting your .270win. Tons of ammo choices and it's a very proven cartridge. Good glass and a good trigger and a bedding job will make any "old rifle" shoot better.I've thought about just pouring more time/money/tools into my .270 and giving it another year for things to normalize.
I actually just called two local stores and one had "zero 6.5 prc" although the lady kept telling me about 6.5 creed and 6.8spc, it wasn't quite unnerving but enough to raise my doubts. The other store has 6 boxes. I will admit that I really don't shoot much so I wont go through much ammo.