I don't have any problem with .308's efficiency at 200-300 M.
However. I doubt that Op's rig is an adequate combination (accuracy wise) for 200-300 meter hunting. You see, he has discussed his gun + scope in another thread and posted pictures. Like me, he is shooting an 18" barrel scout gun with a 4x scope. Personally, I do not feel comfortable to take such a shot at 300, specially where shot placement really counts, due to the size of the game, caliber or lower velocity to begin with (short barrel).
But that is only me. I am sure many hunters can take that shot comfortably.
My optic is 7x magnification not 4x... I am not worried in the slightest about being able to make a vital shot at 300yards with my rifle.
All I am worried about is velocity loss from the shorter barrel and I have never hunted with .308.
I'm gonna buy a few different brands and test them out see what kind of velocities I get with the different bullets.