Have you removed the rebound lever itself?? The rebound spring goes in FIRST,and is of course pinned in place. Then,isung padded long nose pliers,compress the rebound spring with one jaw on the sprom\ng and one on the frame of gun,between front strap of grip frame and the trigger guard.
This has worked for me,and I've owned(2 currently) a "few" of these "left wheelers".
Bud