The slide on my 9mm XDM 3.8 Full-size started failing to lock back a couple of months ago. I replaced the guide rod spring (the big spring under the barrel) with another guide assembly from Springfield but that had zero effect. Instead it just kept getting worse. Today it started jamming. The slide won't go back far enough for the brass to eject. You can only shoot one round at a time. Weirdly enough, it will successfully eject if there is one round in the gun and lock back about half the time.
I have about 12,000 rounds through the gun. I clean it every time I shoot it. I have replaced the striker spring and striker safety spring but that was general maintenance. I don't see how that could be causing this problem.
Yeah, something is worn out and needs to be replaced, but I have no idea what. It's going into the shop but those guys never explain exactly what went wrong (plus taking eight weeks to get the gun back), and I imagine this is something simple for the experienced gun owners around here. I'd just like to have some idea what's wrong.