From everything I've noticed, including both target practice and autopsying a pig that I shot at very close range, the jacket separates from the core almost every single time when using Hornady XTP rounds in my .44 mag. The pig was shot with a reduced power load with a bullet speed slow enough to see the round passing through the air. The pig is dead, but I won't be using these rounds anymore for hunting purposes.

I've noticed similar separation of the core and jacket when using Hornady LEVERevolution in my .45-70, but those rounds were shot at a steel target. You can't expect too much out of a bullet in that circumstance.