The bullet will have enough punch to do the job at that range. The question is whether the shooter can place the bullet in the right spot. At distances approaching a quarter of a mile there are a lot of things that can happen. For instance there may not be any wind where you are but there may be wind where the elk is and wind can make a difference. Also at that range the flight time of the bullet will be long enough that the elk can take a step which means the bullet won't hit where you want it. Like I said, the cartridge is capable. the question is: Are you?

I grew up shooting a 7mm Mag and I've taken and seen taken more than 120 elk and in my experience there really isn't any reason to push the envelope and take shots at over 400 yards. Too easy to blow it and it isn't too hard to get closer unless you're shooting across a canyon in which case I direct your attention to my comment on wind.