I use a 7mm Rem Mag. It'll reach out there and poke stuff, but I think it's more fun to get as close as I can to the elk. When the elk are in the timber during the day the farthest shot you'll probably have to take is 150yds. The farthest I have shot an elk was 350yds in the wind out on the desert. I caught a herd feeding in a large meadow down off the mountain just before dark. I had to crawl on my belly for a half hour to get in range it was so open.