MAC,
Both Phil Shoemaker and I have experience erratic performance on deer with the 160 Hornady RN--both from 6.5 M-S rifles at traditional velocities. Don't remember exact results that Phil had, but mine included the bullet breaking both shoulders on a mature whitetail doe, and exiting--and another on a similar-sized doe with a behind-the-shoulder shot where the bullet didn't even reach the far ribs.
Might also add that I'm big fan of spitzer Hornady Interlocks....
I have a theory about this. It has to do with the hardness of the core compared to the jacket. I remember reading that the 160 6.5 rn specifically had a harder core than other 6.5 Interlocks for deeper penetration. It makes some sense that the 6.5 160 might be unique in this regard as its a heavy for caliber bullet in a fairly small caliber with a decent chance of being used on truly large game. This leads me to believe that this bullet may shed its jacket early when it doesn't meet enough initial resistance such as bone or heavy fur/hide/muscle. If the lead core is too tough the jacket might peel off early ruining both wounding and penetration. But, its all just a theory.
