I concur with Jame B. on this. There are a variety of suitable rounds. I always used a 7mm magnum myself. I chose it simply in case I needed to shoot at a bit longer ranges. This never happened, in fact. the longest shot on Elk I ever took was about 240 yards. In my experience, a .30/06 would have done just fine. Even a .308 would have been acceptable. I mention this because it is pertinent to your consideration. That is, the maximum range at which you might shoot - this is the most important consideration. You mentioned 50 to 350 yards, I believe. Well, at 250 yards or less, you have a huge choice of rounds. Many will do just fine, though personally, I'd go with something 7mm or larger. Beyond 250 yards, the choices narrow somewhat. If you intend to shoot Elk at ranges beyond 250 yards, in MY opinion (and I shall NOT participate in any arguments on this - other opinions may differ), then I would consider the .30/06 as a minimum. That would do just fine. You don't necessarily need a magnum round, even beyond 250 yards. However, if shooting Elk beyond about 350 yards, (again, in MY opinion), I would then choose a magnum....7mm, the various .300 magnums, .338, etc.

As to what maximum range you plan for - that is up to you. As I said, in my particular (actual) experience....something like a .30/06, a .270, .308, etc. would have sufficed. However, one cannot always be sure of getting closer than 250 yards. I have never trusted myself beyond 250 yards - so I have always made it a point to get closer than that, or forego the shot. I was perhaps lucky, in being able to do that for all three of my Elk kills. In making your decision, you need to consider this issue carefully.

One other thing. Whatever round you choose, it would be best to be sure to use a "premium" bullet. There are many different types that will work. I always used the Nosler Partition, with good results. But, do use good ones, by all means.