Chambering A Round Inserting The Mag; M&P40c XDs SD9VE

I recently realized that when you insert a mag rapidly into a mag fed polymer handgun, at least the mag fed handguns that I own, the slide automatically closes chambering a round. It may just be with enough force the slide lock will release on almost all mag fed handguns, but the M&P appears to be designed with this feature in mind.