Why the '06 over 308? Or even the 7mm. Or a 6.5?
Today 06:46 PM
With elk on the option list a 30-06 is as close to the ideal all around rifle as it gets. It'll shoot the same bullet weights as 308 about 100-200 fps faster depending on the exact load and bullet weight. A 308 will do exactly the same thing, 50-100 yards closer. In a standard size and weight rifle there isn't much reason to choose a 308 over 30-06. The exception is that a 308 can be made in a much lighter, more compact rifle. My Kimber 308 is still under 6 lbs scoped. In steep rugged terrain giving up 100 fps for a rifle that is 2 lbs or so lighter isn't a bad idea.
I have to say I am surprised. I expected suggestions of .300 and up.
Just as a 30-06 will give you 100-200 fps over a 308, one of the 300 magnums will give you 200-300 fps more speed than a 30-06 with the same exact bullets. At under 400 yards no game animal will ever notice the difference between the 3. The 308 starts to lose enough speed after around 400 yards that bullet expansion may not be enough. A 30-06 will give you 50-100 more yards before this is a factor. The 300 mags will add another 100 yards of so to the effective range of a 30-06.
The question is, at what range can you hit an elk? And how much recoil can you tolerate.
A stout load from a 308 or 270 will hit you with 17-18 ft lbs of recoil
A stout load from a 30-06 will have around 20-21 ft lbs of recoil
A 300 magnum will vary from around 25-30+ ft lbs of recoil. There are at least 1/2 dozen 300 magnums and it varies.
But to be perfectly honest, any of the popular chamberings from 7-08 and up will kill elk. The bullet you choose and where you place it is more important than the caliber. A 270 loaded with good quality 150's or a 7-08 with 140's would be just fine if you wanted to go lighter.
Roberts 375 wouldn't be my choice, but it'll certainly work. Choose something you like and will enjoy using.