failure to fire
Excuse the lack of proper terminology, I don't want to keep hitting my back button to get it right. Nontheless, I put Wolff springs in my model 15, 640-1, and model 12. I did have a fail to fire in the model 12 using factory ammo and the reduced power spring -- I installed the lightest of the 3; and if I have any more non-fires, I'll put in the standard Wolff. I'll run a couple boxes of ammo thru it next time at the range.
What really amazed me is how accurate my shooting was with the 640-1 (38+p) with the Wolff springs installed!
And I shoot double action only, for the most part, with my revolvers.