Like greg said, the problem with the .338WSM is that they were falling way short of the .338WM's performance. Slightly smaller bore improved the performance (raised velocities and pressures from what I understand, without sacrificing much bullet weight). It was speculated at the time that between these two is the borderline for performance from the WSM case...to keep up the performance, they've got to change the case, either make it fatter or make it longer, but then it wouldn't be a WSM...I guess the 8mm bore did quite well with this case design, I've heard rumors that the case design was actually best off with a .319" or .320" bullet for optimizing case performance, but that's just what I've heard, no one's seen that in signed print yet.

Personally, I don't think any moose or elk are going to notice whether it's a 8mm round or a .338 round thumping into their side and ripping their heart in half.

I'd be interested to see how this thing does. Might make for interesting bear and bighorn fodder.