Well, I've got an amazing 870 police magnum that I normally use without extension because of a simple, annoying problem. The factory Remington +2 extension that I have (which was mounted on a 870 express and perfectly fitted on it), seems not to like very much my 2013 produced 870 police. What do I mean? The extension screws onto the mag tube with no issues, but when I install its original clamp, the extension starts to bind and diverge a little bit and then I come up with an extension that works, that's properly screwed on but is not parallel to the barrel. What is the problem? Is the police magnum barrel thicker than the express one? The shotgun works and feeds even with this annoying bug but I can't stand that fu**ing bent extension on my gun. Please tell me hot to solve this problem!