I'm trying to find information on my M&P 15 Sport 2 that I recently purchased. I entered my serial number on Smith & Wesson's serial search page, but it said that my serial number is not valid..... Am I missing something? The serial number is the two letters followed by five digits on the outside of the mag well, correct? Could anyone help me find information on my new rifle? I apologize if I sound quite ignorant. This is my first Smith & Wesson and my first AR-15.