I've owned a ranch and been an outfitter in Northwest Colorado since 1994 and have witnessed hundreds of elk kills during the last 27 years since my family first bought our ranch up there back in 94'. Elk are tough, just plain and simple, any way you wanna slice it. I've seen them shot with everything from 6mm's to 378 Weatherby's. If your planning on regularly shooting elk at distance (over 700-800 yards and beyond) on a regular basis each year, and your wanting not just to "successfully kill" them but instead help insure that you don't loose any from marginally placed shots (wind can affect bullets exponentially especially when we're talking about ranges around 1,000 yards and beyond) then you really need to be concentrating on either a .338 caliber or a .375. 338 RUM, 338 Norma, 338 Lapua, 340 Weatherby, or even the new 33 Nosler shooting 250 grain bullets with muzzle velocities of 2,900 fps or higher or heavier bullets with even better BC's slightly slower. My personal favorite would be the 33 Nosler with a 28" barrel loaded with 250 Elite Hunters at 2,950 fps if I wanted to keep rifle weight under 11 or 12 pounds. I have killed several elk myself around the 450 yard range using just a factory 375 Ruger guide rifle firing 260 Accubonds at 2,750 fps. Everyone of my kills using the 375 Ruger with that load were bang flops. If I didn't mind extra weight and was firing from a fixed position where I'm not having to carry it very far, hunting maybe on a private ranch like i do most of the time then I would step things on up to the 338 Norma, 338 Lapua, or the best in my opinion for a heavier fixed position rifle would probably be the .338 Terminator built by Defensive Edge with a 30" fluted barrel firing 300 grain Berger's close to 3,100 fps. The 7mm's and especially the 300 mags with heavy high BC bullets will do the job for sure, but for long range elk thumpers (thumpers not just successful killers) the 338's and 375's just give you the kind of performance that true long range elk hunters are seeking. Just my opinion after watching several hundred elk kills with various calibers over the past 27 years of guiding elk hunters.