Not trying to be insulting here, but is there some reason why you feel it necessary to shoot +P rounds in your Shield? It was not intended or designed to use that ammo, and in my experience it is not necessary. I believe your owner's manual recommends against that type of ammo. Even if your Shield shoots it without problems, +P ammo is much harder on it and will likely shorten it's lifespan. The recoil spring is designed for standard pressure ammo. Do (or did) your mags remain in place when shooting standard pressure ammo? If so, that's a clue!

__________________
So long ... Ken