I have a Smith & Wesson 629-1 .44 Mag revolver. The problem is that sometimes while firing it single action the cylinder will not rotate to the next round. The hammer will go back, but when the trigger is pulled...click. The hammer falls on the just fired chamber. It seems to happen mostly on one chamber of the cylinder, but I am not sure of this. It has been to a couple of gun smiths but the problem remains. Any ideas are appreciated. Jim