My opinion is any S&W in proper condition made after WWII is fully safe with plus P. If you started shooting a box of plus P a week, the added pressure might, just might start getting the gun loose to the point of needing repair, in about a half a century. I also hold the opinion with the exception of a few rounds to confirm poa and poi and function once in a while if you carry plus p, there is no good reason to shoot plus P otherwise.