Originally Posted by sgtlmj
All Glock RSAs fall out of the assembly notch the first time the slide is cycled. That's why if you just take the slide off without disassembling it further, you need to make sure to push the RSA back into the notch before returning the slide to the frame.
I understand that they do move slightly out of the notch; but, I think this one came out further than normal because it appeared to be what hung up. It was only after I was able to re-seat it that the slide came off. It wasn't easy to re-seat (difficult to get fingers in there). I may be wrong; but, I can't think of any other reason, based on the "gouge" and the fact that slide came off easily after I re-seated the RSA.
Also, I am positive that it was properly seated before I shot it. I always check on all my Glocks to make sure the RSA is properly seated before I put the slide back on. It is habit.
EDIT: Although I am "positive" that I properly seated the RSA before firing, I am imperfect, and I could have screwed up that time.