Your comments are understandable.
I own a pair of M&P 340's, myself, which are not quite 2 ounces heavier than your PD (13.3oz v. 11.4oz), thanks to a steel cylinder, and Magnum loads are still rather robust, to say the least.
I even changed the grips to the standard boot grip on one of my M&P's, adding about an ounce to its weight, and it's still a handful.
While I used enough Magnum loads to find some which didn't exhibit bullet pull in my gun, being fired in my hands, I typically use +P loads for normal training, quals, practice & carry (with some occasional standard pressure loads thrown in for practice, when they're available at the right price).
Congrats on the 340PD. Handy lightweight J.
Take the time to read the safety manual regarding ammunition selection & testing. The minimum bullet weight restriction in Magnum loads is intended to help reduce the potential for premature erosion of your cylinder face & charge holes (because of the titanium cylinder).
Also, don't use cleaning practices and materials that can damage the titanium cylinder's surface.
These lightweight Sc snubs are strong, and can slip into pocket holsters and 'disappear', weight-wise. Handy.