My own impression is that the question posed by the OP has been answered and that the poster has a significant set of information available to use to inform his decision.
Carrying on with the off-track discussion:
The folks making the claim that the 6.5mm FMJ did not cause the head injury have likely not shot many gallon water jugs with FMJ bullets.
If that bullet starts to tumble right after entry, an awful lot of energy gets transferred.
Another scene many of us have seen is of the Viet Cong prisoner executed by a Vietnamese General the morning after the General's family was murdered by the Viet Cong. While the TV news channels did not show a closeup of body afterword, the dynamic coverage suggests that the damage was in much the same class as JFK's head injury. The shot by the General was with, I understand, a snub-nose .357 which has far less velocity and energy than the Carcano.
So yes, the damage from the FMJ is plausible.