How do you break down a S&W Model 539 semi auto for cleaning?

1)Remove the mag and check for an empty chamber.

2) Pull the slide about halfway back, so that the holdopen notch in the slide is behind the halfmoon shaped piece on the slide stop.

3)Push the slide stop out from the right side of the pistol and totally remove it.

4) Ease the slide assembly forward and off the frame.

5)Turn the slide assembly over, grab the spring and rod assembly, and pull it forward and slightly up, to get the collar of the rod out of its retaining notch in the bottom of the barrel.  Then pull the spring and rod assembly out of the slide.

6)Turn the slide back right side up, and the rear of the barrel will drop down somewhat.  Move the barrel about a half inch or so forward and the rear will drop down some more. Wiggle the bck end of the barrel around until you can pull it to the rear, away from the slide.

The pistol is now field stripped and all normal cleaning operations can be performed.

If the above instructions weren't clear enough, call S&Ws 800 number (sorry, don't have it right here) ask  for Customer  Service, and they'll sen you a set of instructions with pictures.