Personally, I would like to have a .338 Winchester Magnum for elk hunting. I hear a lot of people extolling its virtues. On the other hand, I don't have a .338 Win Mag now, and most of my money is going to college tuition money for chilrden these days and not to adding guns to my cabinet. My .30-06 shooting 180 grain bullets dropped a 4x4 elk in its tracks this past October -- as well it might given the shot was at less than 100 yards and the bull was oblivious to what was in store for him. I would feel no insufficiency going elk hunting again with my .30-06. I think the .338 Win Mag may give greater authority at long range -- say 300+ yards -- but I'm not sure my shooting skills qualify me for taking such long shots. Thus, the .30-06 probably is fully sufficient for my needs. Additionally, I'm not hunting for trophys and am not likely to run across a really big bull elk that might take more killing.
I guess I would say that if I were to buy another rifle for elk hunting, I would try to find a .338 Win Mag that pleased me. But this is in the context of already owning two .30-06 rifles, which I'm not planning on letting go of.
.284s or larger would be my choice. Plenty of heavy-for-caliber bullets available from this point on up, especially in premium array. Though I would like to see what a fast, heavy .264 would do.
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I think the three you mentioned are great. For most people, including myself, their trusted deer rifle would suit them fine for elk, they just need to pick the proper bullet. A well manufactured, heavy for caliber, and well constructed bullet from your average deer rifle will do great on elk.
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