I assume you are talking about Hornady factory loads and not reloads. I and another friend have found Hornady to be very hot ammo. I recently fired some in a 25-06 barrel that flattened the primers more than I am comfortable with. In addition, the expansion ring at the web was swollen more than Remingotn 100 grian PSP loads.
That you have split necks makes me question the conditon of the chamber. If we are speaking reloads, it makes me question the condition of the brass. If in fact it is Hornady factory ammo, I'm not surprised, Every lot of that stuff I've seen runs right at the ragged edge of max pressure. Break opens actions are known to be springy, I'd stay away from ammo known for being hot.