A couple of things come to mind ref the lock up of the action as the hammer comes back in DA.
Look at the sideplate (for contact) and the area inside the frame near the back of the bolt, to see if there are any signs of contact from the hammer. Sometimes the "tail" of the hammer (see photo) can catch on the edge of a protruding bolt stem, or the edge of the cutaway in the frame made for the bolt itself.
Also, if the sear is not long enough, when the trigger cams off of the sear, and transitions over to the DA bevel on the hammer, it doesn't go under the bevel as it should but strikes the hammer bevel face. This is usually felt as a "bump" when it first begins to malfunction due to wear. When parts are switched, however, this can manifest itself as a complete stoppage, and not just a "bump".
You should be able to see and feel this happen if you remove the sideplate, remove the mainspring and strut, and then cycle the action slowly, adding some gentle forward hand pressure to the back of the hammer at the spur, paying attention to the area where the top of the sear ledge of the trigger transitions contact from there over to the DA camming surfaces on the hammer and trigger. If the camming surfaces are striking head-on at that location, a longer sear would be needed. If the transition is functioning correctly, the DA cam on the hammer should come in above the DA bevel on the trigger. The malfunction may be happening because you have substututed a used part into the mix. The part may have in fact, been sold after having been removed from another j-frame because it was malfunctioning in this way.
That's the reason why you're having problems. You can't just "drop in" these parts. They are fit to each particular gun.
