If this forum existed in 1935 there would have been thousands of posts asking "why do we need this 357 magnum?". It's just going to shake my N frame to pieces. Everyone is making 10's now and there are lots of factory choices for ammo. One of the aspects of introducing new calibers that no one ever talks about is that it brings attention to the platform. Someone reading an article in American Rifleman about the new 10mm M&P may not want a 10 but it might make them look at the gun in another caliber. I would not be surprised at all if Smith introduces an M&P in 10mm.