Been carrying my Shield for a while, had not done much dry work with my M&P 9C for a while. I noticed when I dry fire it, the slide shifts to the left and slightly clockwise when it fires. It rattles if you shake it. Normal? It has a few thousand rounds through it, but not an extremely high round count. Problem, or just a broke in pistol? It moves enough you can see it in the sights, I hold the gun steady, and the slide moves... I emailed S&W, but always like to tap into more knowledge here on the forums than I have.