I know they have done studies on adequate penetration of different shot sizes. I don' t believe this included the HV loads that are now available. But they found that #6 shot out of a magnum turkey load had adequate ft/lbs for reliably killing a turkey out to 35 yards. If I remember correctly #5 shot out to 42 yards and #4 out to 46 yards. I may be off by a foot or two on the #4 shot. But I know the #6 & #5 shot info is correct.

I would guess that the HV loads would by you a few more yards but I don' t know exactly how many.