Doc,
Replacing the rebound slide spring is pretty easy, actually.
1. Remove the side plate.
2. Remove the hammer spring.
3. Remove the hammer by pulling the trigger enough to release the hammer, then move the hammer back by hand. When it clears the frame, lift the hammer up off the hammer pivot stud.
(now comes the intersting part...)
4. With a flat bladed screwdriver, very gently lift up on the back of the rebound slide until the top coil of the spring clears the reboundslide retaining pin.
Go slowly! If you go too fast, and the spring completely clears the retaining pin, it will shoot out with pretty good force.
5. Take a shop rag to pad your thumb, and hold it over the rebound slide spring. The idea is to hold it in such a way that you won't have the spring come shooting out.
6. With your thumb in place, holding the spring to keep it from flying out, use the screwdriver to finish prying the rebound slide up and over the retaining pin.
7. Remove the rebound slide, and take the spring out of the slide.
Depending on the age of your gun, there MAY be a pin running through the center of the spring. Not all of them have this, though.
8. Put the new spring into the slide. Put the pin back into the spring, if one was there.
9. Another tricky part. You need a Phillips screwdriver with a head that is just slightly larger than the loops on the spring.
10. Set the rebound slide into the frame so that it is properly aligned with the ball stud on the trigger.
11. Put the Phillips into the rear of the spring and push in to compress the spring so that it will clear the rebound slide pin.
12. Push down on the rebound slide so that the bottom loop of the spring catches on the rebound slide pin.
13. Remove the Phillips screw driver, and using the flat bladed screwdriver, push the top loop of the spring in so that it clears the rebound slide pin, and push the rebound slide down until it is fully seated.
14. Replace the hammer.
15. Replace the side plate.
And you're done.
It sound difficult at first, but once you've done it a couple of times, it gets a LOT easier and quicker.
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Beware the man with the S&W .357 Mag.
Chances are he knows how to use it.