Regarding the slide stop issue:
When most people are handling firearms, they drop the magazine before locking the slide to the rear. However, at many gun shops they just check the chamber before handing the gun to a customer; they leave the empty magazine in the weapon. If the customer ends up locking the slide to the rear, they are often surprised by the amount of pressure it takes to press the slide release with an empty magazine inserted.
0331: "Accuracy by volume."