Old J. Stevens 12 ga pump breakdown help

[kamflyer]

I have an old J. Stevens model 520 pump that I am trying to take down. According to everything I have seen and heard, the procedure is to unscrew the magazine tube, then the magazine and barrel assembly will slide down in the receiver, then when the slide is moved forward, it should disconnect and separate.
I get the magazine tube unscrewed, the assembly slid down and the slide moved forward but it still won't disconnect. It hangs up on something.
Am I missing something? A hidden catch somewhere maybe?
Suggestions welcome.
Thanks -Rob-

 

[kamflyer]

Took another look in better light and found the problem. Someone at some point in time had replaced a pin at the muzzle end of the magazine tube. The slide was hanging up on it and not allowing it to move forward far enough.
-Rob-