Thanx Mikey, et al
I did call S&W and the rep suggested firing it to see if that would take care of the problem. No mention of any free mags (darn). BTW, the S&W Walthers only carry a one year warrenty since they are not S&W's, just made by S&W.
Anyway, after hanging up I field stripped again just to look at the slide stop, etc again. Now the slide does stay retracted on the empty mag. Maybe just a bit of residue in there, somewhere.
Mark