I've had the same problem when asking about Winchester Deer Season Copper Impact. I bought several boxes because they were the only .308 ammo I could find recently to try out in a new rifle.
I've only found a few online experiences with them on deer (all positive reviews), but not enough people using them to get a good idea of how they perform on animals larger than deer.
An email to Winchester ammo got a reply saying they were designed for deer but they should work well on elk.
