Tom, is this lockup dependent on the orientation of the revolver. Such as does it happen when the revolver is level but not when it's pointed up or down? If this is the case I would suggest that you check to see if there is a pin inserted inside the Rebound Spring to act as a trigger stop. If there is, flip that pin end for end and this should solve your problem.

Note, the N frame revolvers typically have in trigger stop in inside the rebound spring and I discovered the orientation of this pin is rather critical. Because get it installed the wrong way and the result can be exactly what you are experiencing. BTW, if you've read between the lines and feel that I learned this lesson the "hard way" you would be 100% correct. Since I don't own any J frames I didn't mention this before but thought it may be helpful in the event your model has that trigger stop pin installed.

I will also repeat my suggestion that you purchase the Kuhnhausen Shop Manual. Even Rocket Scientists use manuals so I really don't see the logic in beating your head against the wall when a manual can be such an asset.