Hi,
I shoot +P out of my M&P 38 special made in 1954. No issues. The round I have used is the Buffalo Bore 158 gr +p LSWCHP. This round is about the most powerful factory round for 38 special out right now. Velocity runs 1100 FPS or more out of a 4 inch barrel. Most +P rounds run about 900 FPS.

regards,
roaddog28