Removing Slide Without Barrel and Spring Installed

I was doing some general maintenance on my G17 yesterday. I put the slide (without barrel and spring) on the slide. Without the spring the slide moved freely and reset the trigger. I had a time getting the slide off the frame. The slide moved forward to a point and hit resistance and wouldn't move any more forward. I fiddled with it and finally one time when I pulled the trigger the slide jumped forward and came right off.

Did I make a bad move putting the empty slide on the frame?...

Removing Slide Without Barrel and Spring Installed