I hunt with a 6" GP-100 on odd occassions, and I usually have it with me on my rifle hunts. In my experience a .357 is not good for a quartering-through-the-bones shot with any load. I had great results with my 125gr Rem golden sabre duty (he-he...doody!) loads, as well as 158gr JHP, and even Win 110gr JHP. Federal 180gr hard cast (in their premium hunting line) gave FMJ like performance, which was okay at the time because I was putting down another hunters crippled WT doe and did not want to tear up alot of edible flesh.
What these deer all had in common was UNOBSTRUCTED ENTRY INTO THE HEART AND LUNGS. If I were going to recomend something, it would be a JHP of 158gr weight. 125s might be OK, but steer clear of the 110gr. I admit it really is too light. Also dump the cast bullets. They will kill...but slowly.
No matter what you choose, you MUST choose to pass up poor shots, and that may mean shots you could have taken with a rifle.