Sorry, Bill, I have seen the difference!!
A premium bullet is one which is constructed well enough that it will penetrate through heavy bone and other tissue to reach the vitals from any reasonable angle without disintegrating or shedding it's core completely.
I have had a couple of dramatic failures using the Interlocks when I tried to drive them at high velocity and hit bone.
One, a 270, 140 BTSP @ 3000 M.V. completely disintegrated on hitting a Deer's rib, with no part of the bullet making it in to the cavity. Fortunately, a quick follow-up did him in. If he had got out of sight quickly, I am sure he would have been lost. [Initial shot was 75 yards]
Another 180 IL from a 30-338 at 3100 fps M.V. struck a calf moose on the shoulder blade, and disintegrated, not penetrating the blade at all. It knocked the guy down, but he was up immediately with a saucer size shallow wound on that shoulder. Again, a second shot thwarted his escape. [Initial shot was 110 yards]
I know from personal experience with Partitions [100+ head of game shot] that both those incidents would have been one-shot deals.
I have shot at least 5 moose quartering toward me that took a 180 Partition right on the shoulder bone and penetrated completely through the lungs. Recovered a couple, others exited.
Most of the time, the Hornadys work fine. But with two failures for me, they are now relegated to practice and low velocity rounds.
REgards, Eagleye.