I've shot both of my .338 WM's practicing across canyons using small objects as targets. As long as I know the distance (usually by laser rangefinder, but sometimes estimation) I've found the .338's are easily capable of MOA accuracy out to farther than I would like to shoot game. I've shot very small rocks at 700 yards without too much trouble.
Now, rocks aren't what you asked about but I include that just to show what is possible with a little practice.
The longest shot I've made on game with my .338 was last year's elk. I shot a spike elk across a canyon at almost exactly 600 yards. Two of the shots were in the shoulder and you could cover with a small cup and the third was just 4-6" behind the others on the same level in the lungs.
Just like any rifle you want to use for long range work, being able to know you distance pretty accurately and knowing your ballistics from practice makes it possible. The .33's have plenty of energy at extended ranges to take game cleanly. If you need more, there is always the .338 RUM, if you're up to the practice time with it.....
Bob
