I have been hunting elk in Idaho since I was 12 years old. I'm on the far side of 43 now. I did not get my first elk until I was 17 years old. I think it took me that long to learn a little more about elk hunting. Since then I have only gone three years without getting an elk.
I started hunting with a 270. After a few years, and one heck of a tough old cow, I moved up to a 7mm. 7 years ago I set up a 300 RUM because my hunting changed to cross canyon shooting for elk in the
Timber. The 7mm was stretched to it's limits in my opinion and I DO NOT like losing elk. I have not looked back since.
My two sons started hunting with a 270s. Between the two of them they have harvested 9 elk since 2010.
One thing that has always rang true with me and elk hunting with a .270 and 7mm is to break leg bones. I have learned it's better to put one down and get another shot into it, then to get a lung shot and take a chance on the elk getting away. I hate to see them suffer, but I hate worse to lose one after shooting it.
Elk are very tough and sometimes it's hard to tell if they were even hit because they hardly flinch at all. Since using my RUM I have shot 6 elk and not one of them has required a second shot. My farthest to date, with this caliber, is 586 yards. One of the years I didn't get an elk was the last year I had 7mm. I'm proficient with it at 700 plus yards. I had a nice bull ranged at 709 yards. I was by my self and I chose not to shoot because I believed if I had hit it, but did t drop it right there, then there was a huge risk of me losing him in the timber. I believe in the 1500 Ftlb rule for elk as I've witnessed time and again elk being hard to kill.
I do believe there is something to be said about an "elk caliber". That is all relevant, in my opinion, to how far away one is from an elk and shot placement.
This year my wife shot a nice cow at 199 yards with a 7mm-08. I heard the bullet hit, but didn't see the elk flinch at all. She ran about 30 yards with the rest of the heard. She stopped and as my wife was getting ready to pull the trigger again, the elk fell. Seconds later she was dead. The shot placement was behind the shoulder, through the lungs. That's her picture above with her "unicorn hunting rifle".
In the end I would suggest to anybody to shoot a heavier caliber with premium bullets. That's just my opinion and I'm know there are many others out there with a ton more experience than I have.
I like reading these forums, because, like every hunting trip, I still learn new things.