The NBT I have used have been a bit erratic. I only recall one exiting and at least on lost its core with the jacket found under the hide on the offside.
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I have pointed out here (and elsewhere) that often core/jacket separations don't mean nearly as much as many hunters apparently believe. The most extreme examples were two bullets that lost their jackets at the ENTRANCE hole on medium-sized buck deer, one a 130-grain Sierra GameKing from a .270 Winchester, and the other a 105-grain Speer Hot-Cor from a .243 Winchester. In both cases the core went on into the deer and killed it.
Another one that apparently puzzles many people is Ballistic Tips. Quite frequently the jacket is all that's recovered--but usually from the opposite side of the animal. (Or at least that's where I've always found them.) But in Ballistic Tips the jacket generally weighs as much or more than the core--the reason the jacket penetrates deeper when they separate.
Haven't found one in a while though, the last a 100-grain .25 from a .257 Roberts, from a mature Montana doe whitetail shot at 50 yards quartering toward me. The bullet broke the shoulder joint, and the jacket was found under the hide at the rear of the ribcage on the opposite side.
