If you want to see how this action works, you might take a look at an e-book by Gerard Henrotin titled, "Colt New Service Revolver Explained". He takes you step by step through the action, or the rebound system, the hammer safety, and the sear (hammer and trigger). Once you learn this, you can see what needs to be done to tune one of these. I admit that you have to hand fit some parts, but really, I never found it that hard on these, even building cam surfaces back up to get them to operate properly. Take your time, and it can be done, but learn the action first.