I purchsed NIB XD9 about 3 weeks ago. Yesterday I had a chance to go to the range. I fired about 100 rounds and there is one thing I'm concerned about: There were several occasions when the slide didn't lock after the last round was fired. It came with 2 mags and I tried both and it kept happening with both of 'em. I went to Academy where I bought the Pistol at and one of the guys who worked there told me that some new XDs have problems with the mag. My XD was manufactured in Jan 2009. He offered 50% off on a Promag magazine for my new XD9. I didn't want to buy another mag cause I paid the full amount and I want the original mag to work. I was researching this issue on internet and I found this link : http://www.thefiringline.com/forums/showthread.php?p=2758801 My thumb may be touching the slide lock button.. I may need to work on that but I can't test it until I go to the range next time. My question is has anyone experienced the same problem with their new XDs? Also if I need to buy a new mag for this thing to work properly what are the reports on the Promag brand? I would appreciate your suggestions. Thanks for your time!