I shot a 180lb whitetail with an iron sighted 357 Mag GP100, 6in barrel at 35yrds. Broke the shoulder and went through both lungs. This was using factory Remington CoreLokt 165gr hunting ammo.
Don't let anyone tell you the 357Mag is too small but be realistic with the distance. Set a reasonable one and stick to it. You should also hold out for a good shot, mine was stepping very slowly and broadside to me. If he was walking away, running etc I would not have taken the shot.