TheKid,
The Pointed Soft-Point Core-Lokts were changed around 1990. Before that they had heavy "sidewalls" in their jackets, which combined with the cannelure tended to hold them together pretty well. But after 1990 they had thinner jackets--except for the round-nose models, which retained the thick jackets. Or at least they did for several years. I haven't sectioned any in a while.
That said, even the heavy-jacket Core-Lokts could come apart if they hit heavy enough bone. I shot a facing mule deer buck with a 180 from a .30-06 around 1980, and while it killed the deer, the bullet turned into fragments on the buck's spine. Also, John Nosler (the original designer and maker of Nosler Partitions) shot a British Columbia moose in the shoulder with a Core-Lokt from his .300 H&H, and the bullet failed to penetrate beyond the shoulder. Nosler eventually killed the moose, but that experience led him to develop the Partition--which he first field-tested on another moose, and worked fine.
