I was disassembling my Mossberg 590 the other day and when I was about to put it back together I spot this little metal piece on the table that I have no idea where it came from or where to put it back. It's cylindrical about 3mm in diameter and about 6mm long. I've gone over all the pieces 5 times but I don't see a hole or anything where something like this would go. Can anyone help me? I'll post pictures of the other parts if needed. Any help would be greatly appreciated, thanks!!