I use to get lots of stovepipes with my Shadow with handloads that would shoot just fine through an M&P... definitely a spring issue.
The Shadow comes with a 15# spring, which is just a tiny bit weaker than the standard CZ-75 16# spring (hence the "weakened recoil spring" advertized on their website and such as a feature of the pistol). The 75 is a military pistol designed to fire hot military rounds. You put a round even a little weaker than a factory round through it and you'll note that the casings barely spit out and will sometimes not clear the slide before it slaps forward and stovepipes.
When shooting for practice with full power reloads, I use a 15# spring (the standard one). When shooting weaker competition reloads for practice, I use a 13# spring and when shooting competition reloads in competition where I really don't wanna risk a failure, I use a 11# spring.
I've never had a failure to load with mine, or a double feed that wasn't due to the stovepipe.