For an elk rifle I would choose a 30 or 338 caliber cartridge. I would determine what the max range is you feel you can accuratly shoot in the field. I would choose a cartridge that delivers 1800 ft/lbs energy with a heavy for caliber bullet at that range.

I only feel comfortable to 500 yards and hunt with an 06 for elk. A 300 WM is good to around 700 yards and a 338 win mag is good to around 800 yards. Your hunting altitude and bullet choice will also affect the effective range quite a bit.

I hunt at 10,000 feet elevation and my 06 can deliver over 1800 lbs/ke at 650 yards using the 200 grain accubond which is more than adaquate for elk.