S&W revolvers lock up on the cylinder bolt and the hand. They lock up on the thickness of the hand. The little tip of the hand is locking up on the cylinder ratchet portion of the extractor. In the past, for an older revolver, I bought a replacement hand. I was lucky, it was a little thicker, so it fit pretty well and tightened things up. If the replacement is too thick, it will have to be carefully thinned to fit. It is a job probably best left to someone who knows what he is doing.