When I carried a 642, I loaded it with the Speer 135-gr. +P’s. When I changed to an M&P 340, I initially loaded it with the Speer’s. I’ve since changed to the Hornady 158-gr. XTP’s. The Speer’s were very uncomfortable to shoot more than a few cylinders of.
I run the Speer short barrel load in my M&P 340. It was that or the Buffalo Bore load and I couldn’t find that locally.