If I could only have one rifle then that would mean that I did not have much money-so whatever I chose, I would have to be able to shoot it on the cheap.
So I think I would probably choose a single shot like the High Wall or the Ruger #1. And the cartridge would either be 30-40 Krag or 358 Winchester. If I did alot of elk hunting it would be the 358. If I only did a little elk hunting then it would be the 30-40 Krag.
The reason for my choice is simple. They would be very inexpensive rifles too shoot. For example the 30-40 Krag is a fantastic cast bullet cartridge because of the long neck. It is a better cast bullet cartridge than the 30-06, and velocities will be the same in a cast bullet. And since I did not have any money I would definitely be casting my own bullets. Also the 30-40 Krag brass is rimmed and is fairly hefty. So I would get long case live with cast bullets in the 30-40.
Remember now we are talking utilitarian rifles because we cannot afford a second rifle. And we have to keep it simple.
The 358 would be my choice if I elk hunted alot because of the larger cast bullets, and brass would be cheap. So that would be my other choice. Tom.