I knew a guy that took elk with a 25/06. It can be done.
For deer, I've never been big on big guns. I have been using my .308 last dozen years or so when I rifle hunt. But, last year I got the old .257 Roberts out and sighted it in. Actually, it just shot it. It's been sitting since I got that .308 and it's still spot on.
Love that .308, but I just wanna get the old .257 out for use. I may not hunt with it, will be bow hunting this year, handgun hunting, and maybe some trips with the Hawken front loader. The .257 or any rifle feels like cheating out where I'm hunting. 150 yards is a long shot on my land.
I've taken a few deer with a 7mm rem mag hunting out west. It's okay for shooting mulies across New Mexico canyons, but it just seems a bit much even for that. The .257 will shoot nearly as far and kill mulies just as dead, ditto the .308. But, I ain't sellin' the 7. It's fun to shoot, makes a big bang, increases testosterone production. LOL