One of mine was in the recall S/N range too...a new .58cal flint barrel they built for me back in the spring...GM told me they went to a new thread tapping process for nipple seats and vent liner seats, and discovered that the height of the threads may not be as high as they should be, with thread edges more rounded than as sharp as they should be...worried about possible blowout, sent me a prepaid UPS call tag...said if that's the case on mine, they'll replace the breech plug.