I am currently using the 170 gr and have had good sucess so far, the only deer I have shot with it did penetrate a shoulder(my bad), but really didn't open up that much. I didn't measure, but smaller than a .45 exit hole. I have had bad luck with everything that isnt BB ammo, including winchester's 180 gr hunting load. I got one last year with a 158 gr BB that was a perfect shot and it did exit and with a fairly good blood trail. So, if they aren't opening that much, I wanna be sure it comes out the other side so I can find the deer. And I'm still movin up to a 44 next year.
I have a red dot on my gp100 and it makes adjusting the sights easy for the rest of the year when it usually eats .38's for practice. I think the 180 gr wouldn't be bad on deer, but the hp's will work if you pick your shots like you should with the 357. I tried the 170 gr trying to improve groups too, and I couldn't tell a real difference in that and the 158 gr ammo. Good luck and good hunting.