Unless we're talking about blasting prairie dogs, jacket/core separation is a failure. Whether or not it killed the target animal is really irrelevant. I've had big game bullets come apart and regardless of the result, I stopped using them. I've had XTP's come apart in SIMTEST so you can bet your hind cheek that I will not be using them on game. Conversely, I've driven Gold Dots way too fast and had them come apart but the core and jacket never separated.