I used to holster my GP100 with 180gr hardcasts when on my property in northern Minnesota, but have switched over to my G20 SF. They both will work fine but there's something nice about having 15 rounds available vs 6. I do reload so I can load fairly hotter than the run of the mill factory watered down 10mm loads available. But you can, as mentioned, purchase premium ammo to fit the bill.
10 mm gets my vote though.