And, correct me if I'm wrong; the back of the 16 carrier is ramped where the 15 is more squared off, it seems that the 16 carrier would have less impact on the hammer as it rides back. Also on the 15 carrier it appears that the firing pin is more exposed. On one guys' AR, it would fire a couple shots then hang up. You couldn't do jack with it except remove the mag, bang the butt on the ground to get it into battery ensuring a fired/empty chamber then pulling the rear pin and getting it opened up. Everything appeared fine. Close it, repeat, and it would eventually hang up again. Finally figured out that the 15 bolt carrier left too much of the firing pin exposed and it would routinely hang up on the hammer (out of spec or collection of tolerances?). He sent it back to big A for a refund.