I have had this problem in the past. Fixing end shake, a good cleaning and replacement of cylinder stop spring did it for me. I went with heavier spring though not sure if it did any good. I think end shake was the biggest culprit. I currently have ten -2 or older 29's and do not have this problem with any of them. I do not shoot much over 240 grain at 1100 fps in any of them. My late models get the hot stuff if needed these days. Really not needed though for me.