Hi again,
Your 686, 6" barreled .357 has a lot of potential to be a tackdriver.
Shooting it supported (sandbags, etc.) from a good shooting bench, it should be able to hold a 3 shot group WITHIN 2" every single time you do YOUR job.
Now how that translates to "field" accuracy will vary greatly depending upon the skill of the operator. But first, you'll have to dial in your chosen hunting load for a POA distance (probably either 35 or 50 yards depending upon your area you will be hunting.
My 6" barreled S&W Model 29-5, which is a big framed revolver that looks a lot like the smaller 686, is in .44 Magnum caliber but its accuracy is also quite similar to the .357 you'll be hunting with. Both handguns can be excellent on deer.
I STRONGLY RECOMMEND A GOOD RED DOT SIGHT for hunting.
- No, NOT a scope (you'll get worried about the "shakes" when you see the barrel wiggling until you get the shakes out of your hands).
- No, NOT the iron sights, for the accuracy goes totally out the window if there's any mis-alignment between the front blade and the rear sight . . . and deer are about like 2 year-olds . . . they ain't gonna stand there forever as you focus only on your front sight!!!
A red dot sight shoots the bullet to that point so it is super-fast in the field, so you can spend your brain power looking for other things . . . twigs and branches in the way . . . locating the perfect impact spot on the deer . . . making sure the rack is the right size, etc.
For us guys getting ah-hem, "older" too, the red dot sight makes it a lot easier in all light conditions vs. using iron sights.
ADDED BONUS . . .
The speed of the red dot sights allows you to make some incredible shots pretty fast. I dropped a big doe, running broadside in a fresh clear cut . . . at sixty-five yards once. I'd just dropped a FIRST one . . . and that second one took off! Both fell directly down and never moved!
Then, a buck stood up (not seen in the clear cut) and started nuzzling the first deer . . . so I dropped it too. Three deer in mere seconds. No way could I have done this with a rifle.
On another hunt, I took three deer in a deep bottom the same way with my handgun! Lots of great memories through the years as a handgun hunter.
Here's the kind of accuracy your gun should be capable of:
FROM THE BENCH . . .
My M29 is ALWAYS under 2" groups at 50 yards. Always. Here's a typical target, shot at a homemade target of a 5" square:
IN THE FIELD . . .
I'm more proud of THIS target . . . I just shot ONE target that day, to confirm that my red dot sight was still zero'ed with my hunting round before the 2008 hunting season began. IT WAS!
This target was shot at 50 yards too, but STANDING and totally unsupported for FIVE rounds. Yep, a two handed hold of course.
Well . . . actually I fired six shots . . . for I KNEW the second round went of a little low, though I couldn't see its impact. So, I shot six rounds instead of five and the second round was a "called flyer."
No, it isn't sub-2" . . . but it is FIELD accuracy that is great for this many rounds from a 6" revolver. BTW, I sight my M29 for a 75 yard zero. Five rounds into 2 3/4" inches ain't bad . . . now if I could have avoided that second round!!!:
Here's my 1989 M-29, topped with a first generation Bushnell Holosight. Lots of deer taken with this revolver thorough the years. BTW, the hide beneath the revolver is from a rare Piebald (white-spotted) Whitetail buck taken with this revolver:
Here's my latest result with this rig, on Nov. 4th:
Hope this helps! Gotta run out to the deer camp now . . . I'll be in the stand in the morning with my M29!!!
Tom