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.
Let me start by telling you the story of two Johns.
John number one went on a day hike with a couple of friends in the Cascade Mountains about an hour from Seattle. He somehow got separated from his buddies and became lost. John was dressed in casual cloths for a warm weather day hike and had nothing but a lunch with him. He spent three days in those mountains and luckily made it out to tell the story.
John number two, a friend of John number one, was much better prepared when...