Well I got one of these guns in the 24" flavor and shot quite a bit with it this week, performed great. Just took it apart to clean it and once it was back together I noticed I had an extra part....
A small O-ring was left sitting on the table and I have no idea where it came from. It looks very similar, if not identical, to the O-ring that is on the firing pin retainer. Any ideas?
EDIT: Mystery solved, found a schematic on Brownells. It is, in fact, an identical O-ring but goes on the firing pin itself. Did not notice it I removed the firing pin spring.