The original Corelokts had, like the Peters Belted bullets, an inner "belt" , a thickening of the jacket, that served to hold things together and increase penetration. They were regarded, in the heavier weights like the 180 .30 cal, as the hot setup for big stuff like elk, moose and griz.
In 1998, I shot a good-sized 8-point whitetail through the shoulders with a 180 .30/06 Remington factory load at maybe 100 yards. He reared up like a horse and fell over backwards and was dead when we got to him. As it was very warm, and there was a tricky steep, descent to face, I didn't do much of a post-mortem, but there definitely wasn't an exit wound, which I thought was strange for a "moose bullet" used on a deer.
Some years later I read an article by Mule Deer that the inner belt had been abandoned as a cost-cutting measure. At a later date, I seem to recall reading that perhaps they never existed at all. If someone has some vintage Corelokt ammo and would be willing to sacrifice one for sectioning, we would know the truth.
As a side note, that buck was really rutted up, with a hugely swollen neck, and stunk to high heaven. It also provided some of the finest tasting venison I've ever had. So much for the fable that rutting bucks aren't good to eat; at least whitetails.
