Gabby,
Kirby describes the WC's performance quite well. The comparison with the conventional cup jackets is appropriate.
In my 270 Win, i've taken deer at long and close range. Long range with the Sierra 130 boat tail. Bullet went in the front and lodged under the hide ahead of the off side ham. Perfect expansion with lead retained.
Short range with a Nosler ballistic tip. Deer was facing kind of away # 110 yds. Bullet entered between the rear ham and rib and hit that little bone sicking down from the spine, crossed through the vitals and lodged in the hide at the off front shoulder. Bullet looked exactly like the LR Sierra with the jacket being curled back to almost the base. Just a small piece of the core was retained, which fell out when the bullet was handled.
All in all the performance was good with both bullets. I would expect the WCs to be as good or possibly better.
Blacktail,
It's gonna be pretty tough to get in touch with Richard.