Buy a spring kit. Has main spring and 3 rebound slide springs.
Most folks end up running the middle rebound spring.
Polish the sliding surface of the rebound slide. Make sure overtravel pin in rebound slide doesn't have a burr on it. Might be radiused one one side but just cut on the other.
No prob there, but if you install it backwards the spring can catch on the non radiused edge.
Knock off the edge (give it some sort of bevel) and it won't matter which way it goes in.
Saw a minty 29-2 that'd hang up. Orig owner just put it away.
Heir traded it to shop, said it was messed up. Rebound slide pin was the problem.
I was offered the gun, malfunctioning for a good price. I took it in the back and fixed it for the shop.
Like stainless rigs better.
Rebound slides are a bit nasty. Pinched fingers the norm. I use a brass rod (with rounded end) for pushing out compound bow axles- has handle. It is perfect for pushing the spring in when reinstalling the slide.
Also, don't pry on the sideplate to remove. There's no excuse to dinging stuff up nowadays with Brownells/ Midway and many other Youtube vids available.
Of course, some vids are perfect examples of what not to do LOL.
Your gun is fairly new. Shoot the crap out of it. That might be all that's needed. I've had three 629's and never needed a spring kit. But then I hunt and run them single action.
I did however radius the sides of the trigger............but these were all -3 and older so did not have the case hardened triggers. My 4" was pretty nice in double action, only issue is being an N frame............just too big for my hand.
Your L frame.............I'm on the hunt for an older 686 4"myself.
Nice rig!