IMO the primary duty when hunting with a handgun is to make a humane kill. That means you don't take a shot at a range beyond your ability or the capability of the gun/caliber.

I'm also not buying that a 686 is capable of a 2 inch group at 100 yards, every test I've ever seen indicates that it's a 2 inch shooter at 25 yards, not 100, and that's from a fixed machine rest.

If the OP wants to take a deer at 100 yards, I would suggest using a rifle or something with more power, like the 460 magnum. To be blunt, the 357 Magnum lacks energy at 100 yards to insure a clean kill unless the hit is just perfect and the 686 isn't accurate enough to get that perfect hit. I would suggest you limit your range to 25 yards where the 686 has both the energy and accuracy to do the job well.