I have the 300 rum and it is a very accurate round. The 7mm should be just as good. It would be best suited for heavy bullets of great construction because of high velocity. It will kill anything you need to kill... period! The recoil is strong but with practice you will find it manageable. Ammo is expensive but if you reload it is not such an issue.
As good as the core locks are, in the magnums I would go at least a 150gr bonded bullet. Your asking a lot for a 140gr bullet to stand up to that velocity at the closer ranges. Matter of fact, I'd look for a 160gr load if it were me.
The corelokt ultra should be fine as it's a premium bullet but i to would suggest the Nosler Partition. I use 160gr Noslers inmy 7 Mag for just about everything. The 150gr Scriocco is also a good bullet for long range shooting. I would try a couple of different loads & see which one shoots the best in your rifle.
Bring them in on a string. I love this term, if you want to be successful on calling in Elk, try not to just sound like the other caller. We all laugh at each other when we are practicing Elk calling at home or while camping. When I first started calling in Elk, I had no idea what i was doing and it's funny how many I could call in. The biggest Bull that I have called in to date was actually my first. I was making cow calls and screwing it up big time. But it's obvious I didn't screw up...