I had purchased an M&P 15 sport during Christmas and ended up ordering the cali complaint version due to low stock of the standard version. I had thought the only difference would be the mag size witch is an easy fix (just buy a larger mag), but I was wrong, In Cali not only do they have a 10 round mag limit but they also require that your mag release be swapped out for a bullet release (A bullet release requires you to stick the head of your bullet or a thin object into the whole on the mag release to remove the mag). I did not know this when in purchased the rifle and at first thought my mag was just stuck in the rifle. When I figured out what was wrong I called my local gun smith who was an idiot and told me I cannot switch out the bullet release and would have to replace my entire lower receiver. Before I took the plunge and purchase a new lower receiver I decided to give S&W a call and the gunsmith told me that was ridiculous. He told me all you need to do is drill out the current bullet release and purchase a mag release and simply screw it in. So in short I ended up fixing the issue for $20 as appose to $300. My rifle is now a standard AR-15 sport.