The 10 ring on McKenzie targets has been one of my pet peeves for the past 14-15 years. The 10 ring is the last place I' d aim on a live deer. It' s not designed to the idea of getting people used to good hunting shot placement. It' s designed to let 3D shooters get a high score. If they miss the 10 low, they' ve still got an 8. If the 10 was at the bottom of the chest like it would be for a heart shot, they' d get a 5 if they missed low. The 10 ring is in the exact spot we used to shoot for a ' safe' shot in the days before 3D, when the 10 point heart shot was at the very bottom of the kill zone. LIKE IT SHOULD BE.

Anyway.... The center of the 10 is at least 5" too high, and is actually closer to the spine than it is to the heart. If your deer squatted the least bit as the arrow was in the air, then that explains the curled tip on the broadhead and the poor penetration. You probably didn' t whack the spine itself. More likely angled into the thickest part of a rib. And, like Kip said, that shoulder blade is still a possible culprit.

Definitely go and look for him to make sure, but I doubt you got inside the ribcage. He' ll be back.