I'd not recommend a 6.5 PRC for 4-500y on ELK(we have over #1000 elk here), I have a 26 Nosler, and 6.5-284(virtually the same as a 6.5 PRC). I've used a 270 WSM on a few ELK, it worked fine. The 7RM(I have 2) is similar in performance but has the advantage with bullets above 160g(my 270wsm ELK load is 165g Matrix at 2915fps). 300WM has a little more performance and heavier bullets- more than enough for 500 yards by a ways, kicks more and rifle usually weights more. I usually carry my 270WSM and sit with my 300RUM. If I were to pick a new caliber and rifle the 7mm PRC is interesting.