I tried that, and while the 5906 slide worked fine in the 6906 frame, the 6906 slide absolutely will NOT work on the 5906 frame.

It 'feels' like the unlocking lugs aren't engaging the barrel properly: there is a VERY heavy 'catch' trying to cycle the slide. As in at first I couldn't get the slide to move more than about 1/4th of an inch! I thought it was on for good!

It was all I could do to pull the slide back, so I could get the slide stop out!

I remember doing this with a 669 and a 659, and firing them at the range.

I don't understand why this won't work my 3rd gen S&W's

Any idea, guys?