On the 686 you would do much better getting a pre-lock model. It will keep its value even as a shooter and you can get a nice one still for much less than a new lock model.
Also, not sure why you want a 6". Not much gained in accuracy IMHO and the power increase is negligible. The 4" is much more portable, especially when going hunting. You may like to take it when you go bow hunting for hogs as a backup where allowed ...
Talking about shooting small pigs - you can see it done here along with a bunch more of ..357 S&W wisdom. Nice video as always from hickok45 ...
George
Smith and Wesson 686 - YouTube