Rafsob,
As I remember it the Big Boar Took a .570 diameter ball 279 gr and heavy ticking worked well with it greased.
The 58 caliber Maxi 555gr and the hunter 560gr.
Now I am not sure but I though the maxi and the hunter were discontinued.
The max load was 120gr.
My own experience with one gun shows the PRB working the best both for group and for trajectory.
Its has been a long time since I sold all my 58's and when to 54 caliber for the flatter trajectory and the drop them on the spot capability.
Hope this helps some. Lee