I installed the wolff reduced power mainspring and 13lb recoil spring in my 629. It is like a new gun, the action was always pretty smooth but now it is much better and lighter. I have not had any issue with light strikes and have used many different primers. To me it was certainly worth the $10. Since the K frame hammer is lighter you may need a heavier recoil spring to keep it reliable but the beauty is they supply three.

Try it and see, if you don't like it then put the stock parts back in or pay for a proper action job. There is very little risk and high reward. Make sure it works with your preferred ammo and you are good to go.