Yeah, there is no "bonding" in the Hot-Cor. I have even sectioned bullets and the core falls right away from the jacket.
That said, there is nothing wrong with them, though some lots of bullets can have spotty accuracy due (I assume, again from experience sectioning them) to occasional bubbles in the lead core, which don't do anything for accuracy.
If I recall correctly, I have taken big game with many different Hot-Cores, including the 105-grain 6mm, 87 .25, 100 .25, 140 6.5mm, 150 .270, 130 7mm, 165 .30, 200 .338 and 270 9.3mm. Only one that I know of ever separated core and jacket, and that was a 105 6mm from a .243 that hit a whitetail buck at about 250 yards. The jacket was found at the entrance hole, but the core went on inside and killed the deer. At the other extreme, a 165 from a .30-06 killed another whitetail buck with a rear-angling shot at about 150 yards. That bullet was recovered from the far shoulder, retaining 85% of its weight and looking like a magazine ad.
Impact velocity has not been over 2800 or so with any of them, even the 140 6.5mm from the .264 Winchester Magnum. Indeed, muzzle velocity has rarely been much over 2800. That is one key to performance with any traditional lead-core bullet.
I must also point out that the boattailed bullets in Speer's line are NOT Hot-Cor, but are swaged with a relatively soft lead core. They tend to be a little more accurate but also don't hold together as well, which I suspect has nothing to do with the boattail but instead the softer core.
