I have a Mossberg 500 waterfowl edition. The gun has performed flawlessly all season until last week when it began malfunctioning. I thought it might have something to do with moisture, ice, cold etc. and being dirty, but even after a full teardown, clean, and lube it is still acting up. It will work fine at first, but as the day wears on it begins to malfunction. What happens is the first shot fires fine, I cycle the action to eject the empty (which it does) and reload another shell from the magazine (which it does), but then when I pull the trigger nothing happens. The trigger pulls back, but doesn't fire the shell. I have to cycle the action very hard to get it to eject the second shell (unfired), and then the third shell fires fine. This makes no sense to me. Does anyone have any ideas?