If you have already replaced the springs, including the mainspring, it's likely a headspace problem. The rear gauge should be .060" - .064"....measure with feeler gauges between the rear of the cylinder and the breechface. You don't indicate the dash number of your model 60, but along with measuring for end shake on the cylinder, be sure to check for end shake on the yoke as well. (older models made prior to spring and plunger yoke screw mod)

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Ret. LE, FA Instr, S&W Armorer