I started out with a .243. I've killed whitetail, antelope, and mule deer with it. I'm trying to remember, the counts... i'm thinking 3 whitetail, 2 antelope, and 2 mulies. I've never shot at an animal with it and not recovered that animal. All were recovered within reasonable distances (a deer can run fairly far even after a vital shot).
It is absolutely enough gun for these animals. I've since switched to a .270. As always, it's all about shot placement. A well-aimed .243 is much better than a misplaced .270.
As for load, I just used Remington Core-Lokt 100 gr. Any hunting load should do, just find one that's accurate and you're good to go.