I have a Bersa Thunder 9 Pro 9mm. I've shot over 500 rds and I've never had a jam, miss fire, or any other problems. But yesterday I had a spent casing stay in the barrel so that my slide locked open as if I were out of rds. What would make that happen all of a sudden? I'm still pretty new in the hand gun department but I feel I know enuff. The weapon has been cleaned and oiled regularly after I shoot. The last time I shot was in june. I have also been using the same ammo also for about the last 200 rds. Thank you for your feedback.